A  SYSTEMATIC  TREATISE  ON  THE  OCULAR  MUSCLES, 


BY 


G^c.  SAVAGE,  M.D., 

Professor  of  Ophthalmology  (Defects  of  the  Eye)  in  the  Medical  Department  of  Vanderbilt 

University,  Author  of  "  New  Truths  in  Ophthalmology,"  and  "  Ophthalmic  Neuro- 

Myology,"  Ex-President  of  the  Nashville  Academy  of  Medicine,  Ex-Presider.t 

of  the  Tennessee  State  M.edical  Association,  Ex-President  of 

the  Southern  Medical  Association. 


EIGHTY-FOUR  ILLUSTRATIVE  CUTS  AND  SIX  PLATES 


SECOND  EDITION 


PUBLISHED  BY 
THE  AUTHOR,  137  Eighth  Avenue,  North,  Nashville,  Tenn. 

PRINTED  BY 
McQuiDDY  PRINTING  COMPANY,  Nashville,  Tenn. 

1911.  (i) 


o 


Entered,  according  to  Act  of  Congress,  in  the  year  1902, 

BY  THE  AUTHOR,  G.  C.  SAVAGE, 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington. 

Revised,  reprinted,  and  re-copyrighted 

BY  THE  AUTHOR,  G.  C.  SAVAGE, 

July,  1911. 

(ii) 


PREFACE  TO  THE  SECOND  EDITION. 


The  bringing1  out  of  this  edition  has  been  delayed  two 
years  longer  than  the  author  had  intended,  the  first 
edition  having  been  practically  exhausted  three  years  ago. 
He  trusts  that  the  delay  has  served  to  make  this  book 
both  more  interesting  and  more  convincing.  The  first 
chapter  has  been  enlarged  by  the  addition  of  ninety-one 
pages;  but  one  hundred  and  thirty  of  the  one  hundred  and 
forty-five  pages  of  this  chapter  have  been  newly  written. 
This  chapter  has  been  enriched  by  the  addition  of 
twenty-three  new  illustrative  cuts,  every  one  of  which 
helps  to  make  the  light  of  truth,  as  the  author  sees 
it,  shine  the  more  vividly. 

For  twenty  years  the  author  has  been  at  a  disadvan- 
tage in  that  his  teaching,  concerning  the  fundamental 
principles  of  ocular  rotations,  has  not  been  in  accord 
with  that  of  the  immortal  Helmholtz.  The  contrast  is 
shown  in  the  parallel  columns  on  pages  32  to  34.  The 
whole  of  the  difference  between  the  teaching  of  Helm- 
holtz and  that  of  the  author  hinges  on  the  correct 
answers  to  the  following  four  questions:  (1)  Is  the  cen- 
ter of  the  cornea  always  the  anterior  pole?  (2)  Is  the 

(iii) 


iv  PREFACE. 

central  point  of  the  macula  always  the  posterior  pole  of 
the  eye?  (3)  Do  all  secondary  visual  lines  cross  the  vis- 
ual axis  at  the  nodal  point?  (4)  Do  all  secondary  visual 
lines  cross  the  visual  axis  at  the  center  of  retinal  curva- 
ture— the  center  of  rotation?  To  question  (1)  Helmholtz' 
answer  was  "yes,"  but  the  author's  answer  is  "no;" 
to  question  (2)  the  author's  answer  is  "  yes,"  but  Helm- 
holtz'  answer  was  "no;"  to  question  (3)  Helmholtz'  an- 
swer was  "yes,"  but  the  author's  answer  is  "no;"  to 
question  (4)  the  author's  answer  is  "yes,"  but  Helm- 
holtz' answer  was  "no." 

The  unbiased  reading-  of  the  first  chapter  of  this 
edition  will  convince  the  most  skeptical  that  the  central 
point  of  the  macula  is  the  posterior  pole  of  every  eye, 
whether  it  be  the  ideal  or  the  nonideal  eye;  that  the  cen- 
ter of  the  cornea  is  the  anterior  pole  of  the  ideal  eye  only. 

All  related  principles  of  ocular  rotations  stand  out 
clearly  in  the  light  of  the  demonstrated  fact  that  the  cen- 
tral point  of  the  macula  is  the  posterior  pole  of  the  eye. 

The  so-called  "optic  axis  "  of  Helmholtz,  when  not  the 
visual  axis,  as  in  the  ideal  eye,  is  nothing  more  nor  less 
than  one  of  the  secondary  lines  of  vision. 

The  mastery  of  the  fundamental  principles,  set  forth 
in  the  first  chapter,  can  be  easily  accomplished  with  the 
aid  of  the  Muscle  Indicator,  five  times  depicted  in  this 
chapter.  There  is  no  condition  of  a  single  ocular  mus- 


PREFACE.  V 

cle,  or  any  combination  of  the  ocular  muscles,  normal, 
abnormal,  or  pathologic,  which  this  device  will  not  show; 
and  its  construction  is  based  on  the  following1  two  facts: 
(1)  The  center  of  the  macula  is  the  posterior  pole  of  the 
eye;  (2)  all  indirect  visual  lines  cross  the  visual  axis  at 
the  center  of  retinal  curvature,  which  is  the  center  of 
rotation. 

No  book  on  the  ocular  muscles,  except  this  one  and  its 
companion  volume.  "Ophthalmic  Neuro-Myology, "  has 
been  based  on  the  fundamental  principles  set  forth  in 
the  first  chapter  of  this  book.  If  these  principles  are 
not  correct,  this  book  and  its  companion  volume  are 
worthless.  The  author  has  no  doubt  but  that  the  final 
verdict  of  the  scientific  world  will  be:  "  These  princi- 
ples are  veritable  truths." 

The  practical  chapters,  II.  to  XII.,  have  had  such  cor- 
rections and  additions  made  to  them  as  appeared  neces- 
sary in  order  to  make  them  clearer  and  stronger.  This 
is  especially  true  of  Chapter  III.,  to  which  four  pages 
have  been  added.  Everything  taught  in  these  chapters 
is  based  on  the  fundamental  principles  set  forth  in  Chap- 
ter I.;  and  the  value  of  every  procedure  advocated  has 
been  established  by  abundant  practical  experience. 


PREFACE  TO  THE  FIRST  EDITION 
1902 

ART  cannot  succeed  when  principles  are  unknown  or 
ignored.  The  mechanical  or  surgical  art  of  readjusting 
the  ocular  muscles,  when  there  is  maladjustment  or  im- 
balance, should  be  based  on  the  scientific  principles  un- 
derlying ocular  rotations,  else  such  art  should  not  be 
practiced.  These  principles,  as  simple  as  they  are  en- 
during, are  discussed  in  Chapter  I.  of  this  volume,  and 
with  sufficient  clearness,  the  author  hopes,  to  enable  the 
reader  to  fully  comprehend  them.  Without  a  clear  un- 
derstanding of  these  principles,  it  will  be  impossible  to 
grasp  the  teaching  of  subsequent  chapters;  but  in  the 
light  of  the  teaching  of  Chapter  I.,  the  remainder  of 
the  book  may  be  easily  understood. 

Whenever  it  has  been  possible,  in  the  interest  of  truth, 
the  author  has  been  glad  to  agree  with  writers  who  have 
preceded  him;  when  forced  to  dissent  from  their  teach- 
ings, he  has  done  so  cautiously  and  respectfully,  invari- 
ably giving  his  reasons  for  so  doing. 

If  the  aim  of  the  critic — and  the  author  hopes  that 
every  reader  will  be  a  critical  reader — who  may  review 
this  volume,  shall  be  the  establishment  of  truth  and  the 

(vi) 


PREFACE.  Vll 

dethronement  of  error,  he  will  not  become  an  object  of 
terror  to  the  author;  for  he  himself  has  been  laboring1, 
through  a  period  of  fifteen  years,  for  the  accomplishment 
of  the  same  end,  as  it  relates  to  the  ocular  muscles.  He 
believes  that  what  he  has  taught  in  this  book  is  true, 
and  that  practice  based  on  what  he  has  taught  will  be 
correct.  He  would  not  promulgate  nor  perpetuate  error 
if  he  knew  it;  therefore  the  reviewer  who,  in  his  own 
way,  points  out  what  he  may  find  to  be  erroneous  is  as 
much  his  friend  as  the  one  who  may  give  emphasis  to 
what  he  finds  to  be  true. 

In  the  body  of  the  book  the  author  has  given  due  credit 
to  every  writer  and  thinker  on  the  subjects  discussed, 
whom  he  had  an  opportunity  to  consult,  and  it  only  re- 
mains for  him  to  acknowledge  here  the  helpfulness  he 
has  derived  from  their  labors. 

For  the  mechanical  excellencies  of  the  volume,  the 
author,  who  is  also  the  publisher,  is  indebted  to  the 
printing  establishment  whose  inscription  can  be  found 
on  the  title-page. 


ILLUSTRATIONS. 


FIG.    i.  Illustrating  rotation  of  a  sphere 3 

FIG.    2.  The  plane  and  axis  of  a  rotation 1 1 

FIG.    3.  The  left  monocular  spacial  pole  and  field  of  vision 18 

FIG.    4.  The  right  monocular  spacial  pole  and  field  of  vision 18 

FIG.    5.  Rotation  of  the  eye  in  its  orbit 23 

FIGS.  6,  7.  Erroneous  teaching  as  to  poles  of  the  eye  and  lines  of  direc- 
tion        28 

FIG.    8.  True  teaching  as  to  poles  of  the  eye  and  lines  of  direction  ...       28 

FIG.    9.  The  Le  Conte  1882  horopter 36 

FIG.  10.  The  Le  Conte  1898  horopter _ 37 

FlG.  II.  The  equator  and  the  two  axes  of  rotation 44 

FlG.  12.  For  calculating  false  torsion  in  oblique  conjugate  rotations  ...     47 

FlG.  13.  Professor  Daniel's  figure  for  calculating  false  torsion 49 

FIG.  14.  The  fixed  vertical  and  horizontal  planes  of  the  head,  the  two 

eyes  in  ideal  orbits  and  Listing's  plane 72 

FIG.  15.  The  conjugate  and  fusion  brain  centers 93 

FlG.  16.  Isogonal  circle  of  the  author 97 

FIG.  17.  A  section  of  a  wooden  body  representing  the  surface  of  binoc- 
ular single  vision 100 

FlG.  18.  The  primary  and  secondary  isogonal  circles 103 

FlG.  19.  The  Muscle  Indicator  showing  the  eyes  in  their  primary  posi- 
tion      112 

FlG.  20.  The  Muscle  Indicator  showing  the  right  cardinal   secondary 

position  of  the  visual  axes 1 16 

FIG.  21.  The  Muscle  Indicator  showing  the  upward  cardinal  secondary 

position  of  the  visual  axes 1 18 

FlG.  22.  The  Muscle  Indicator  showing  an  oblique  secondary  position 

of  the  visual  axes  without  torsion  (normal) 120 

(viii) 


ILLUSTRATIONS.  IX 

FIG.  23.  The  Muscle  Indicator  showing  an  oblique  secondary  position 

of  the  visual  axes  with  torsion  (unreal  j   122 

FIG.  24.  The  field  of  binocular  single  vision 124 

FIG.  25.  The  field  of  binocular  view 124 

FIGS.  24,  25.  Both   show   the   binocular   spacial    pole,   meridians   and 

parallels 124 

FIG.  26.  Binocular  spacial  meridians  and  parallels,  groups  of,  and  the 

primary  isogonal  circle 131 

FIG.  27.  Shows  that  a  binocular  spacial  pole,  meridians  and  parallels, 
would   be  impossible   if  the  maculas  are  not  the  posterior 

poles  of  the  eyes 138 

FIGS.  28,  29.  The  Stevens  phorometer 149,  150 

FIG.  30.  The  Wilson  phorometer 151 

FIG.  31.  The  monocular  phorometer 155 

FiG.  32.  The  cyclo-phorometer 162 

FiG.  33.  The  Stevens  clinoscope 164 

FIG.  34.  The  Stevens  tropometer 170 

FiG.  35.  Showing  the  retinal  areas  of  binocular  fusion 175 

FiG.  36.  The  Stevens  scissors 249 

FIGS.  37,  38.  The  Stevens  forceps 249,  250 

FiG.  39.  The  Stevens  hook 250 

FiG.  40.  The  Stevens  needle  holder 250 

FIG.  41.  The  Price  tendonometer 254 

FiG.  42.  Retinal  fusion  areas 289 

FIG.  43.  Showing  malformation  of  left  Orbit 343 

FiGS.  44,  45,  46.  Showing  malformation  of  both  orbits 344,  345,  346 

FiG.  47.  Hyperphoric  exercise  set 373 

FiGS.  48,  49,  50,  51.  Illustrating  cyclophoria 391 

FiG.  52.  Illustrating  orthophoria  of  the  obliques 391 

FiG.  53.  Perry's  device  for  taking  cyclo-duction 399 

FiG.  54.  Showing  frames  containing  exercise  cylinders 411 

FiG.  55.  A  square,  illustrating  the  changes  by  non-oblique  astigmatism  421 


X  ILLUSTRATIONS. 

FIG.  56.  A  rectangular  parallelogram,  illustrating  the  changes  by  non- 

oblique  astigmatism 425 

FIG.  57.  A  square,  showing  changes  by  oblique  astigmatism 426 

FIG.  58.  Showing  the  shape  of  a  fused  square  by  one  who  has  oblique 

astigmatism,  most  curved  meridians  diverging 427 

FIG.  59.  Showing  changes  caused  in  lines  not  parallel  with  chief  me- 
ridians of  astigmatic  corneas 429 

FIG.  60.  A  photograph  of  a  rectangle,  made  by  a  non-astigmatic  lens       431 

FIG.  61.  A  photograph  of  a  rectangle,  made  by  an  oblique  astigmatic 

lens 432 

FlG.  62.  A  photograph  of  a  rectangle,  made  by  a  vertical  astigmatic 

lens 433 

FIG.  63.  A  photograph  of  a  rectangle,  made  by  an  oblique  astigmatic 

lens 434 

FlG.  64.  A  photograph  of  a  rectangle,  made  by  a  horizontal  astigmatic 

lens 435 

FIG.  65.  Same  as  Fig.  61,  except  that  the  sensitized  plate  was  not  at 

the  focal  interval 436 

FIG.  66.  Showing  the  retinal  images  of  an  arrow,  when  there  is  no  as- 
tigmatism, or  when  the  astigmatism  is  vertical  or  horizontal  437 

FIG.  67.  Showing  one  horizontal  image  and  one  oblique  image  of  an 

arrow 441 

FlG.  68.  Showing  how  the  arrow  would  be  doubled,  except  for  compen- 
sating cyclotropia 441 

FIG.  69.  Showing  the  minus  cyclotropia  that  has  occurred  for  fusing  the 

two  images  shown  in  Fig.  68 443 

FlG.  70.  Showing  one  horizontal  image  and  one  oblique  image  of  an 

arrow  444 

FIG.  71.  Showing  the  plus  cyclotropia  that  has  occurred  for  fusing  the 

images  shown  in  Fig.  70 445 

FIG  72.  Showing  two  oblique  images  of  the  arrow,  the  obliquity  up  in 

one  eye  and  down  in  the  other 445 


ILLUSTRATIONS.  Xl 

FIG.  73.  Showing  the   minus   cyclotropia   that  has  fused   the   images 

shown  in  Fig.  72 446 

PLATE  I.  Showing  images  and  object  in  non-oblique  astigmatism  and 

in  hyperopia  and  myopia 448 

PLATE  II.  Showing  object  and  images  in  diverging  oblique  astigmatism  453 
PLATE  III.  Showing  the  minus  cyclotropia  that  has  fused  the  dissimilar 

images 457 

PLATES  IV.,  V.,  VI.  Showing  arcs  of  distortion  by  cylinders.   472,  477,  485 
FlG.  74.  Representing  compensating  vertical  and  lateral  heterotropia      491 

FIG.  75.  The  amblyoscope  of  Worth 546 

FlG.  76.  Illustrating  the  first  step  of  the  Fox  operation  for  exotropia  .     577 

FlG.  77.  Illustrating  the  second  step  of  the  Fox  operation 578 

FlG.  78.  Illustrating  the  third  step  of  the  Fox  operation 579 

FlG.  79.  Illustrating  paralysis  of  the  right-vertors 606 

FlG.  80.  Illustrating  paralysis  of  the  left-vertors 607 

FiGS.  81,  82.  Illustrating  paralysis  of  the  sub-vertors 608 

FiGS.  83,  84.  Illustrating  paralysis  of  the  supervertors 609 


CONTENTS. 


CHAPTER  I.  PAGES. 

The  Fundamental  Principles  of  Ocular  Rotations 1-145 

CHAPTER  II. 
Orthophoria 146-179 

CHAPTER  III. 
Heteropboria 180-272 

CHAPTER  IV. 
Esophoria 273-313 

CHAPTER  V. 
Exophoria 314-340 

CHAPTER  VI. 
Hyperphoria  and  Cataphoria 341-381 

CHAPTER  VII. 
Cyclophoria 382-416 

CHAPTER  VIII. 
Compensating  Cyclotropia 417-488 

CHAPTER  IX. 
Compensating  Heterotropia 489-496 

CHAPTER  X. 

Comitant  Esotropia,  Exotropia,  Hypertropia,  Catatropia,  and  Cyclo- 
tropia    497-594 

CHAPTER  XI. 
Paralysis  and  Paresis  of  the  Ocular  Muscles 595-622 

CHAPTER  XII. 
Muscles  of  the  Iris  and  of  the  Ciliary  Body 623-661 

Index 662-684 

(xii) 


OPHTHALMIC  MYOLOGY. 


CHAPTER  I. 


THE  FUNDAMENTAL  PRINCIPLES  OF 
OCULAR  ROTATIONS. 

A  SPHERE,  in  rotation  around  its  center  as  a  fixed 
point,  has  on  its  surface  two  points,  and  only  two  points, 
that  do  not  move.  These  two  points  must  be  180°  apart, 
and  the  straight  line  that  connects  them  must  be  a 
diameter  of  the  sphere.  This  diameter  is  the  axis  of 
a  given  rotation.  Every  point  on  the  surface  of  the 
sphere,  other  than  the  two  fixed  points,  moves  in  a  plane 
at  right-angles  to  the  axis  of  rotation,  describing  the 
circumference  of  a  circle  larger  or  smaller,  on  the  sur- 
face of  the  sphere.  The  size  of  any  one  of  these  circles 
is  determined  by  the  distance  of  the  given  rotating  point 
from  the  nearer  of  the  two  fixed  points  up  to  90°.  A 
point  90°  from  the  two  fixed  points  describes  the  circum- 
ference of  a  great  circle,  while  all  other  rotating  points 
describe  circumferences  of  small  circles.  The  planes  of 
all  the  circles  thus  created  are  rotation  planes,  and  each 


2          THE  FUNDAMENTAL  PRINCIPLES 

one  is  parallel  with  all  the  others.  The  planes  of  all 
these  circles,  except  the  plane  of  the  one  great  circle, 
may  be  ignored,  for  the  plane  of  any  given  rotation  is 
the  plane  of  the  one  great  circle.  This  plane  alone  cuts 
the  axis  of  rotation  at  its  center — the  center  of  the 
sphere — while  the  planes  of  all  the  small  circles  cut  the 
axis  at  varying1  points  from  the  center. 

Only  one  of  the  infinite  number  of  points  lying*  on  the 
great  circle  should  be  studied  in  any  given  rotation,  but  it 
should  not  be  forgotten  that  all  points  on  this  great  circle 
bear  an  unalterable  relationship  to  the  one  chosen  point. 
The  line  extending-  from  the  chosen  point  back  through 
the  center  of  rotation — the  center  of  the  sphere — to  an- 
other point  on  its  surface  just  180°  distant,  is  the  rota- 
ting line,  and  all  other  moving  lines,  whether  diameters 
or  not,  may  be  ignored,  for  all  these  lines  must  bear  a 
fixed  relationship  to  this  one  chosen  line.  Both  the  ro- 
tating line  and  the  axis  of  rotation  are  diameters  of  the 
revolving  sphere.  They  lie  in  the  plane  of  the  same 
great  circle,  and  each  is  at  right-angles  to  the  other. 
This  is  always  true,  regardless  of  the  point  of  applica- 
tion and  the  direction  of  the  force  effecting  the  rotation. 
A  change  in  the  direction  of  the  force  only  means  a  new 
axis  of  rotation,  a  new  rotating  point  and  rotating  line, 
and  a  new  rotation  plane. 

A   careful   study  of   Fig.   1    will  serve  to  fix  in  the 


OF    OCULAR   ROTATIONS. 


mind  the  truths  that  have  been  taught  above.  In  this 
figure,  A-B-D  represents  the  cross-section  of  a  concave 
hemisphere  whose  center  is  c\  in  which  is  set  the  con- 


Fig.  i. 

vex  sphere  whose  cross-section  is  a-d-b-e.  and  whose 
center  is  also  c.  The  lines  a-b  and  d-e  are  diameters 
of  this  sphere,  at  right-angles  to  each  other  and  in 


4  THE   FUNDAMENTAL   PRINCIPLES 

a  plane  common  to  the  two.  Since  this  sphere  is  loose 
in  the  concave  hemisphere,  any  point  on  its  surface  may 
be  chosen  as  the  point  for  rotation.  If  a  is  to  be  rotated 
into  the  position  of  I),  it  must  move  in  the  plane  of  the 
great  circle  of  which  a-b  is  the  diameter.  The  two  fixed 
points  on  the  surface  of  the  sphere  in  this  rotation  are 
d  and  e,  and  the  line  connecting-  them  is  the  diameter 
d-e,  which  is  the  axis  of  this  rotation.  It  lies  in  the  same 
plane  with  a-b  and  also  in  the  plane  of  the  great  circle 
which  is  equally  distant  at  all  points  from  both  a  and  b. 
The  force  so  applied  as  to  make  a  the  rotating  point  and 
a-b  the  rotating1  line,  fixes  the  axis  of  rotation  as  d-e,  for 
d  and  e  are  the  only  two  fixed  points  on  the  surface  in 
this  rotation.  Any  point  on  the  surface  between  a  and 
//  and  between  a  and  n  will  rotate  in  a  plane  parallel 
with  a-b,  each  circle  growing"  smaller  as  the  point  re- 
cedes toward  h  or  n.  Likewise  circles  for  revolving 
points  between  h  and  </and  between  n  and  c  grow  small- 
er as  the  rotating  points  recede  from  h  or  n,  until  at  d 
and  e  the  circle  has  become  infinitely  small,  or,  in  other 
words,  d  and  e  do  not  move  at  all.  The  tangents  at  d 
and  e  are  parallel  with  a-b,  therefore  these  two  points 
are  90°  from  both  a  and  b. 

Again  referring  to  Fig'.  1,  it  will  be  seen  that  the  un- 
broken line  a-b  is  the  diameter  of  the  great  circle  de- 
scribed by  the  rotating  point  a,  the  dotted  line  h-m  is 


OF   OCULAR    ROTATIONS.  5 

the  diameter  of  the  small  circle  created  by  the  moving 
secondary  point  h,  and  n-i  is  the  diameter  of  the  small 
circle  generated  by  the  moving  secondary  point  n. 
These  three  lines  are  parallel,  and  they  all  cut  the  axis 
of  rotation,  d-e,  at  right-angles.  In  like  manner,  an}T 
point  between  a  and  d  or  between  a  and  c  might  be 
studied.  The  point  a  moves  most  rapidly,  while  the 
points  d  and  e  do  not  move  at  all. 

The  force  may  be  so  applied  to  the  loose  sphere  as  to 
make  n  the  rotating  point  and  n-m  the  rotating  line. 
Thus  h  and  i  would  become  the  two  fixed  points,  and 
h-i  would  be  the  axis  of  this  rotation.  By  changing  the 
point  of  application  and  the  direction  of  the  force  on  this 
loose  sphere,  any^  point  on  its  exposed  surface  may  be 
made  the  rotating  point.  The  diameter  extending  from 
this  point  would  become  the  rotating  line,  and  the  diam- 
eter at  right-angles  to  this  revolving  line  and  in  the 
plane  with  it  would  become  the  axis  of  rotation. 

In  any  rotation  of  a  sphere  there  are  three  points  on 
its  surface  to  be  considered — viz.,  the  rotating  point  and 
the  two  fixed  points.  There  are  two  lines,  each  a  di- 
ameter, to  be  considered — viz.,  the  rotating  line  and  the 
axis  of  rotation.  There  are  three  planes  to  be  studied — 
viz.:  (1)  the  rotation  plane,  a  fixed  plane,  in  which  move 
the  rotating  point  and  the  rotating  line;  (2)  the  rotating 
plane,  in  which  lie  the  three  points  and  the  two  lines 


6          THE  FUNDAMENTAL  PRINCIPLES 

(diameters);  and  (3)  the  plane  containing-  the  two  fixed 
points  and  the  axis  of  rotation,  which  also  is  a  rotating 
plane.  These  three  planes  are  each  at  right-angles  to 
the  other  two,  and  the  only  point  within  the  sphere  com- 
mon to  all  of  these  planes  is  the  center  of  rotation. 
The  intersection  of  the  rotation  plane  (1)  and  the  rota- 
ting plane  (2)  is  the  rotating  line.  The  intersection  of 
the  two  rotating  planes  (2  and  3)  is  the  axis  of  rotation. 
The  eye  is  spherical,  the  posterior  half,  at  least,  be- 
ing a  perfect  hemisphere.  (See  Fig.  5.)  It  is  not 
loosely  set  in  the  concavity  in  the  anterior  part  of  the 
bed  of  fat  designed  to  receive  it,  but  it  is  movably 
confined  therein  by  the  capsule  of  Tenon  and  the  mus- 
cles in  which  reside  the  power  for  rotating  it  with 
mathematical  precision  and  with  wonderful  frictionless 
speed.  In  the  eye,  as  in  the  loose  sphere  studied,  every 
rotation  plane  is  the  plane  of  a  great  circle,  and  these 
planes  may  be  many.  The  eye,  unlike  the  loose  sphere 
studied,  has  only  one  rotating  point,  and  this  point  is 
not  anterior,  but  posterior — it  is  the  central  point  of  the 
macula.  The  eye,  having  only  the  one  primary  rotating 
point,  can  have  only  one  primary  rotating  line  (diame- 
ter), and  this  line  is  the  one  extending  from  the  central 
point  of  the  macula  forward  through  the  center  of  rota- 
tion to  the  cornea  at,  or  not  far  removed  from,  its  cen- 
ter, thence  to  be  prolonged  into  space.  This  is  the 


OF   OCULAR   ROTATIONS.  7 

direct  line  of  vision,  or  the  visual  axis.  In  the  study  of 
the  loose  sphere,  the  primary  rotating1  point  was  in  the 
front,  or  in  view,  and  the  rotating-  line  extended  back- 
ward throug-h  the  center  of  rotation.  In  the  eye  the 
primary  rotating-  point  is  behind— is  unseen — and  the 
primary  rotating-  line  comes  forward  throug-h  the  center 
of  rotation  to  the  cornea,  where  it  does  not  stop,  but  ex- 
tends on  into  space. 

As  in  the  loose  sphere  studied,  so  in  the  eye,  there  are 
two  fixed  points  on  the  surface  in  any  cardinal  rotation, 
and  these  are  connected  by  that  diameter  which  is  the 
axis  of  that  rotation.  All  other  points  on  the  surface 
of  the  eye,  not  in  the  rotation  plane,  are  rotated  in 
planes  of  small  circles  that  are  parallel  with  the  rota- 
tion plane,  as  shown  in  the  study  of  Fig-.  1.  All  second- 
ary points  on  the  retinal  surface  bear  an  unalterable 
relationship  to  the  one  primary  rotating-  point,  the  cen- 
ter of  the  macula,  whether  the  eye  be  at  rest  or  in  mo- 
tion; hence  in  the  study  of  ocular  motion,  all  points 
except  the  central  point  of  the  macula  and  one  secondary 
point  may  be  ig-nored.  All  secondary  diameters  of  the 
eye  bear  a  fixed  relationship  to  the  visual  axis  (the  pri- 
mary diameter),  and  all  move  in  perfect  harmony  with  it. 

The  diameters  of  the  eye  are  divisible  into  two  class- 
es, the  rotating  and  the  fixed.  The  rotating-  diameters 
are  divisible  into  two  classes,  the  primary  and  the  sec- 


8          THE  FUNDAMENTAL,  PRINCIPLES 

ondary.  To  the  primary  class  belongs  only  a  single  di- 
ameter, and  it  lies  in  the  plane  of  every  meridian — is  the 
line  of  intersection  of  all  the  meridional  planes — and  it 
alone  connects  the  two  poles  of  the  eye.  To  the  second- 
ary class  belong-  all  other  rotating-  diameters,  each  lying 
in  the  plane  of  only  one  meridian,  but  cutting  the  planes 
of  all  other  meridians  at  the  center  of  rotation.  The 
fixed  diameters  are  two,  and  they  both  lie  in  the  equato- 
rial plane  of  the  eye.  One  of  the  two  also  lies  in  the 
plane  of  the  horizontal  meridian  and  is  the  axis  of  verti- 
cal rotations;  the  other  lies  in  the  plane  of  the  vertical 
meridian  and  is  the  axis  of  lateral  rotations. 

The  primary  rotating  diameter  is  the  visual  axis;  all 
other  rotating  diameters  are  secondary  lines  of  vision. 
The  fixed  diameter,  always  in  the  equatorial  plane,  is 
the  axis  of  a  cardinal  rotation,  and  it,  too,  always  lies  in 
that  meridional  plane  which  is  at  right-angles  to  the  ro- 
tation plane  of  a  given  cardinal  rotation. 

Secondary  rotating  lines  are  divisible  into  two  classes: 
first,  diameters  which  are  secondary  lines  of  vision, 
each  bearing  its  own  relationship,  in  degrees,  to  any 
given  rotation  plane;  second,  the  lines  that  connect  any 
two  directly  opposite  points  on  the  surface,  lying  on  the 
same  side  of  the  rotation  plane  and  equally  distant  from 
it,  but  on  opposite  sides  of  the  equatorial  plane.  These 
two  points,  if  they  do  not  lie  in  the  plane  common  to  the 


OF   OCULAR   ROTATIONS.  9 

visual  axis  and  the  axis  of  rotation,  must  be  on  opposite 
sides  of  this  plane  and  equally  far  removed  from  it.  Such 
lines  are  always  bisected  by  the  axis  of  rotation  and  are 
at  right-angles  to  it,  and  each  lies  in  the  plane  of  its 
own  small  circle,  which  plane  is  always  parallel  with 
any  given  rotation  plane.  These  planes  of  small  cir- 
cles, like  the  rotation  plane  with  which  they  are  paral- 
lel, are  fixed  planes  in  a  cardinal  rotation. 

Lines  connecting  surface  points  not  180°  apart  on 
either  a  great  or  a  small  circle,  should  not  be  considered 
as  either  primary  or  secondary  rotating  lines.  Rotating 
lines  of  whatever  class  are  lines  bisected  by  the  axis  of 
rotation,  but  only  those  lines  that  are  bisected  at  the 
center  of  rotation  are  lines  of  vision.  All  visual  lines, 
whether  direct  or  indirect,  and  the  axis  of  any  rotation 
mutually  bisect  each  other,  and  hence  all  are  diameters. 

The  author's  method  of  finding  the  axis  of  any  cardi- 
nal rotation  as  set  forth  in  the  study  of  Fig.  1  is  simple, 
and  is  applicable  to  all  eyes.  Helmholtz'  method  of  find- 
ing the  axis  of  rotation  is  not  so  simple,  nor  can  it  apply 
to  all  eyes.  It  was  only  in  the  ideal  eye  that  Helmholtz 
found  the  visual  axis  and  his  so-called  ' '  optic  axis  ' '  to  co- 
incide; He  taught  that,  in  the  larger  number  of  eyes, 
the  visual  axis  intersects  his  so-called  "optic  axis"  at  the 
nodal  point.  Since  such  a  visual  axis  could  not  be  a  di- 
ameter, it  could  not  become  the  primary  rotating  line,  in 


10  THE    FUNDAMENTAL    PRINCIPLES 

the  Helmholtz  method  of  finding  the  axis  of  rotation. 
As  will  be  shown  further  on,  Helmholtz  made  a  funda- 
mental mistake  in  his  selection  of  the  center  of  the  cornea 
as  the  anterior  pole  of  the  eye,  constructing1  therefrom 
his  optic  axis,  which  he  carried  backward  through  the 
center  of  rotation  to  a  point  on  the  retina,  usually  be- 
tween the  macula  and  the  optic  disc,  which  point  he 
named  the  ' '  posterior  pole. "  He  should  have  selected  the 
center  of  the  macula  as  the  posterior  pole;  and  if  he  had 
done  so,  his  so-called  ' '  optic  axis ' '  would  have  been  the  vis- 
ual axis  of  all  eyes,  and  the  anterior  pole  would  have 
been  that  point  on  the  cornea  cut  by  the  visual  axis, 
whether  it  were  its  center  or  some  other  point  slightly 
removed  from  the  center.  His  method  of  finding  the  axis 
of  rotation  is  proof  of  the  error  he  made,  for  his  method 
could  apply  only  to  that  eye  whose  visual  axis  cuts  the 
center  of  rotation. 

Helmholtz'  method  of  locating  the  axis  of  any  rotation  is 
fairly  illustrated  in  Fig.  2.  In  this  cut,  a-b  is  the  first 
position  of  the  visual  axis  and  a'-b'  is  the  second  position 
of  the  visual  axis.  The  plane  a-a'-b-b'  is  constructed 
through  five  fixed  points — the  first  point  of  view  b  and  its 
image  a,  the  second  point  of  view  b'  and  its  image  a,  and 
the  center  of  rotation  c.  With  b  as  the  primary  or  di- 
rect point  of  view,  a-b  is  the  visual  axis,  a  being  the  cen- 
ter of  the  macula.  With  b  as  a  secondary  or  indirect 


OF    OCULAR    ROTATIONS. 
01 


11 


00, 


12  THE   FUNDAMENTAL,   PRINCIPLES 

point  of  view,  a'-b'  is  a  secondary  or  indirect  line  of  vi- 
sion, a  being-  the  retinal  image  of  b' '.  The  lines  a-b  and 
a'-b',  each  connecting-  two  points  lying-  in  the  plane,  and 
crossing-  each  the  other  at  the  common  point  c  in  the 
plane,  must,  therefore,  lie  wholly  in  the  plane.  The  ret- 
inal images  a  and  a  are  the  same  distance  apart  in  de- 
grees as  are  the  spacial  points  b-b ',  for  the  arc  a-a  and 
the  arc  b-b'  subtend  ang-les  that  are  equal,  for  they  are 
opposite,  as  shown  at  c.  That  b'  ma}^  become  the  direct 
point  of  view,  the  macula  must  move  from  a  to  a  and  the 
visual  axis  must  rotate  from  b  to  b' ,  to  take  the  place  or 
position  of  what  was  an  indirect  line  of  vision  before  the 
rotation  began.  This  turning  has  been  about  the  point 
c.  The  former  direct  point  of  view  b  has  become  an  in- 
direct point  of  view,  and  its  image  a  is  on  the  retina  to 
the  left  of  the  new  position  of  the  macula.  The  line  a-b 
is  a  new  indirect  line  of  vision.  Truly  the  first  position 
of  the  visual  axis  was  a-b,  but  this  position  is  now  occu- 
pied by  an  indirect  line  of  vision  which  followed  the  visual 
axis  from  right  to  left  through  an  arc  equal  to  the  arc 
b-b' .  Just  as  truly  the  second  position  of  the  visual  axis 
is  a'-&',  for  b'  is  now  the  direct  point  of  view;  but  it  now 
occupies  the  position  of  what  was  an  indirect  line  of  vi- 
sion before  the  rotation  began,  which  line  has  been  ro- 
tated to  the  left  through  an  arc  equal  to  that  connect- 
ing b'  and  b.  The  new  and  the  old  indirect  visual  lines 


OF    OCULAR   ROTATIONS.  13 

have  been  rotated  around  the  point  c  in  perfect  har- 
mony with  the  rotation  of  the  visual  axis.  If  the  plane 
a-a'-b-b'  were  extended  right  and  left,  .it  would  include 
the  line  that  was  the  indirect  visual  line  a'-b'  before 
the  rotation  began,  and  that  other  line  which  has  become 
the  indirect  visual  line  a-b,  as  a  result  of  the  change  of 
point  of  direct  view  from  b  to  b' .  The  rotation  of  all 
lines  has  been  around  the  common  point  c,  and  in  the 
plane  a-a'-b-b' .  This  point  is  the  rotation  center  and 
this  plane  is  the  rotation  plane. 

Helmholtz  found  the  axis  of  this  rotation  by  construct- 
ing1 two  other  planes,  each  at  right-angles  to  the  plane  of 
rotation,  one  of  them  including  the  visual  axis  in  its 
first  position,  the  other  including  the  visual  axis  in  its 
second  position.  The  first  of  these  two  planes,  as  shown 
in  Fig".  2,  is  a-b-f-e,  and  the  second  is  d-b'-h-g.  The 
line  of  intersection  of  these  two  planes  is  c-d,  and  this 
line  is  the  axis  of  rotation.  Since  the  planes  a-b-f-c  and 
a'-b'-h-g-  are  at  right-angles  to  the  plane  a-a'-b-b',  their 
line  of  intersection  c-d  must  be  at  right-angles  to  the  ro- 
tation plane,  and,  as  shown  in  the  figure,  if  extended  up- 
ward, would  cut  the  center  of  rotation. 

In  Fig.  2  the  horizontal  retinal  meridian  of  the  eye  is 
represented  as  lying  in  the  rotation  plane  a  -a'-b-b' ,  with  its 
center  of  curvature  at  c.  In  the  first  position  of  the  vis- 
ual axis  the  solid  line  curve  representing  the  cornea 


14  THE    FUNDAMENTAL   PRINCIPLES 

shows  the  eye  looking-  at  b;  in  the  second  position  of  the 
visual  axis  the  broken  line  representing-  the  cornea  shows 
the  eye  looking-  a.t  b '.  In  either  case  the  visual  axis  gfoes 
from  the  central  point  of  the  macula,  throug-h  the  center 
of  rotation,  c,  on  to  the  point  of  direct  view. 

Fig-.  2  represents  the  rotation  of  Helmholtz'  ideal  eye, 
one  in  which  the  visual  axis  and  the  optic  axis  coincide. 
If  Helmholtz  had  constructed  Fig-.  2  and  had  g-iven  it  a 
close  and  clear  stud}r,  he  would  have  seen  that,  at  least  in 
the  ideal  eye,  all  indirect  lines  of  vision  must  cross  the 
visual  axis  at  the  center  of  retinal  curvature,  which  is  the 
center  of  rotation,  and  not  at  the  nodal  point;  that  they 
are  radii  of  retinal  curvature  prolong-ed,  and  not  the  axial 
rays  of  cones  of  light.  He  would  have  seen  that,  in  the 

non-ideal  eye — the  eye  whose  visual  axis  cuts  the  optic 

« 

axis  at  N,  with  the  macula  at  o — the  line  a-b  could  not 
be  the  visual  axis  in  the  first  position,  nor  could  the  line 
a-b'  be  the  visual  axis  in  the  second  position.  The  vis- 
ual axis  in  the  first  position  would  be  a  line  drawn  from 
o  throug-h  N  to  p,  a  point  in  space  5°  to  the  rig-ht  of  b,  as 
shown  by  the  unfinished  dotted  line  o-p;  and  the  visual 
axis  in  the  second  position  would  be  a  line  drawn  from 
o  throug-h  N'  to  p',  a  point  5°  to  the  rig-ht  of  b',  as  shown 
by  the  incomplete  dotted  line  o-p'.  He  would  also  have 
seen  that,  according-  to  his  own  teaching-,  the  lines  a-b 
and  a-b'  must  be  indirect  lines  of  vision,  as  well  as  optic 


OF    OCULAR  ROTATIONS.  15 

axes,  for  each  crosses  its  respective  visual  axis  at  the 
nodal  point.  He  would  have  seen  that  in  this  non-ideal 
eye  there  could  be  no  point  on  the  visual  axis  that  would 
be  stationary  in  any  rotation  except  the  one  directly  up 
or  down,  for  only  in  such  a  rotation  would  the  misplaced 
visual  axis  cross  the  axis  of  rotation;  and  even  in  the  ver- 
tical rotation  that  part  of  the  visual  axis  within  the  eye 
would  not  be  bisected  by  the  axis  of  rotation.  Such  a 
visual  axis  could  not  be  called  a  "  rotating1  line  "  for  there 
is  no  fixed  point  on  the  line  around  which  it  can  turn. 
All  lines  bisected  by  the  axis  of  rotation  have  on  them  a 
point  around  which  they  can  rotate,  and  that  point  lies 
on  the  axis  of  rotation.  Only  those  lines  that  are  bisect- 
ed by  the  axis  of  rotation  at  its  center — mutual  bisection 
— can  be  lines  of  direction,  or  visual  lines — lines  connect- 
ing- objects  in  space  with  their  retinal  images. 

Reverting  again  to  the  study  of  Fig.  2,  Helmholtz  could 
have  seen  that  the  plane  of  the  horizontal  retinal  merid- 
ian, being  in  the  rotation  plane,  itself  became  the  plane 
of  rotation,  for  the  rotation  plane  in  this  figure  is  noth- 
ing more  nor  less  than  the  plane  of  the  horizontal  retinal 
meridian  extended.  He  would  also  have  seen  that  the 
axis  of  the  given  rotation,  at  right-angles  to  the  merid- 
ional plane  and  cutting  it  at  the  center  of  rotation,  must 
lie  in  the  equatorial  plane. 

Reversing  Fig.  2  so  that  a  shall  be  directly  above  a 


16  THE  FUNDAMENTAL  PRINCIPLES 

on  the  retina,  and  that  b'  shall  be  directly  below  b,  in 
space,  then  the  part  of  the  figure  representing-  the  ideal 
eye  will  be  the  vertical  meridian,  and  its  plane  extended 
would  be  the  rotation  plane  from  b  to  b ' .  Then  the  di- 
rect and  the  indirect  lines  of  vision,  lying  in  the  plane  of 
the  vertical  meridian,  would  cross  each  other  at  the  cen- 
ter of  rotation,  as  they  are  shown  to  de  when  lying  in 
the  plane  of  the  horizontal  retinal  meridian;  and  the  axis 
of  rotation,  at  right-angles  to  the  rotation  plane  and  cut- 
ting it  at  the  center  of  rotation,  would  be  horizontal  and 
in  the  equatorial  plane. 

The  author's  method  of  finding  the  axis  of  a  cardinal 
rotation  of  the  eye,  as  shown  in  the  study  of  Fig.  1,  dif- 
fers in  every  respect  from  the  method  of  Helmholtz,  as 
illustrated  in  Fig.  2.  The  author's  method  found  the 
fixed  points  on  the  surface  which  determined  the  axis  of 
rotation;  Helmholtz'  method  found  the  axis  of  rotation 
which  located  the  two  fixed  points.  By  each  method  it 
was  found  that  the  two  fixed  points  on  the  globe  are  in 
a  plane  with  the  rotating  point  and  with  the  center  of 
rotation;  that  the  two  fixed  points  are  each  90°  from  the 
rotating  point  and  180°  from  each  other,  the  three  points 
lying  on  the  same  great  circle;  and  that  the  line  con- 
necting the  two  fixed  points  is  a  diameter  at  right-angles 
to  the  rotating  line,  which  is  also  a  diameter.  In  each 
case  the  rotating  point  is  the  center  of  the  macula.  The 


OF    OCULAR    ROTATIONS.  17 

rotating1  line  is  the  visual  axis,  and  that  diameter  lying 
in  the  rotating-  plane"with  the  visual  axis  and  at  rig-ht- 
ang-les  to  it  is  the  axis  of  rotation.  By  each  method  the 
visual  axis  is  found  lying-  in  the  plane  of  two  great  cir- 
cles at  rig-ht-ang-les  to  each  other,  and  is  the  line  of  in- 
tersection of  these  two  planes,  the  rotating  plane  and 
the  rotation  plane,  each  being-  a  meridional  plane;  and 
the  axis  of  rotation  is  found  to  lie  in  the  plane  of  a  great 
circle  at  rig-ht-ang-les  to  these  two  planes,  which  plane 
is  undeniably  the  equatorial  plane. 

For  every  eye  there  must  be  a  spacial  pole,  and  it  must 
be  on  the  extended  line  which  connects  the  two  poles  of 
the  eye.  Throug-h  the  spacial  pole  must  pass  the  spa- 
cial meridians,  which  must  be  in  planes  with  correspond- 
ing- retinal  meridians  and  concentric  with  them.  Fig-.  3 
represents  the  spacial  pole  and  spacial  meridians  for  the 
left  eye  and  its  field  of  vision,  and  Fig-.  4  shows  the  same 
for  the  rig-ht  eye.  The  true  spacial  pole  is  always  the 
direct  point  of  view,  therefore  it  must  lie  on  the  visual 
axis.  It  can  be  on  the  visual  axis  only  when  the  center 
of  the  macula  is  the  posterior  pole;  but,  as  has  been 
shown,  and  will  be  shown  ag-ain  in  the  study  of  binocu- 
lar rotations,  the  center  of  the  macula  is  ahvays  the  pos- 
terior pole ',  a  truth  never  grasped  by  Helmholtz  and  his 
followers. 

A  g-lance  at  Fig-.  3  will  show  that  if  the  point  of  cross- 


18 


THE  FUNDAMENTAL,  PRINCIPLES 


OF   OCULAR    ROTATIONS.  19 

ing  of  all  the  spacial  meridians — the  spacial  pole  for  the 
left  eye — is  the  direct  point  of  view,  any  and  all  second- 
ary points  of  view,  in  the  outlined  field,  must  lie  on  some 
spacial  meridian.  The  point  of  direct  view  has  its  image 
on  the  central  point  of  the  macula.  Secondar}T  points  of 
view  on  the  vertical  spacial  meridian  will  have  their 
images  on  the  vertical  retinal  meridian,  and  every  point 
and  its  image  will  correspond  in  relationship  with  the 
spacial  and  posterior  poles;  and  the  spacial  points  will 
be  connected  with  their  respective  retinal  images  by 
straight  lines  lying  in  the  plane  of  the  vertical  meridian 
and  cutting  the  center  of  rotation.  The  same  is  true  of 
points  and  images  lying  on  any  other  meridian.  A 
change  of  the  point  of  view  is  a  change  of  the  spacial 
pole.  This  change  in  the  position  of  the  spacial  pole  is 
accompanied  by  a  corresponding  change  in  position  of  the 
posterior  pole  of  the  eye,  the  latter  coming  under  the 
image  of  the  new  point  of  view  the  moment  the  spacial 
pole  has  reached  that  point.  In  this  rotation  the  visual 
axis  moves  in  the  plane  of  that  meridian  on  which  are 
located  the  two  points  of  view  and  their  two  images. 
The  direct  point  of  view  and  its  image  are  connected  by 
the  visual  axis  which  lies  in  the  planes  of  all  the  merid- 
ians; a  second  point  of  view  and  its  image  are  connected 
by  a  line  which  lies  in  the  plane  of  only  one  meridian,  and 
this  line  is  a  secondary  line  of  vision.  In  any  rotation 


20  THE   FUNDAMENTAL    PRINCIPLES 

the  direct  line  of  vision  moves  into  the  position  of  an  indi- 
rect line  of  vision  around  the  point  common  to  the  two 
lines,  the  center  of  rotation,  and  along  the  plane  of  that 
meridian  on  which  were  located  the  secondary  point  and 
its  image;  therefore  every  rotation  plane  is  a  meridional 
plane  extended. 

The  center  of  the  macula  is  the  rotating  point  of  the  eye 
By  means  of  the  wonderful  muscular  mechanism  of  the 
eye,  the  macula  may  be  rotated  in  any  direction,  but  always 
in  the  plane  of  a  great  circle.  For  this  to  be  possible, 
all  the  great  circles  whose  planes  can  become  planes  of 
rotation  must  intersect  each  other  at  the  central  point 
of  the  macula  and  at  a  corneal  point  180°  removed. 
Great  circles  thus  related  to  each  other  are  meridians, 
and  the  points  of  their  intersection  are  the  poles;  hence 
the  center  of  the  macula  in  all  eyes  is  the  posterior  pole 
of  the  eye,  and  the  point  on  the  cornea,  whether  its  cen- 
ter or  not,  distant  from  the  center  of  the  macula  180°, 
must  be  the  anterior  pole.  The  line  connecting  these 
two  poles  must  cut  the  center  of  rotation,  hence  is  a  di- 
ameter, and  it  must  be  the  line  of  intersection  of  the 
planes  of  all  the  meridians.  This  line  connecting  the  two 
poles  becomes  the  antero-posterior  axis  of  the  eye;  and 
since  the  center  of  the  macula  is  the  posterior  pole,  the 
antero-posterior  axis  is  none  other  than  the  visual  axis. 

In  the  study  of  a  given  rotation  of  the  eye,  in  either 


OF   OCULAR    ROTATIONS.  21 

one  of  the  four  cardinal  directions,  there  are  three  sur- 
face points  to  be  considered:  the  center  of  the  macula 
(the  rotating1  point)  and  the  two  fixed  points  lying-  in  the 
plane  with  it  and  removed  from  it  90°.  There  are  two 
lines  to  be  studied:  the  visual  axis  (the  rotating1  line) 
and  the  axis  of  rotation,  which  connects  the  two  fixed 
points,  and  is,  therefore,  at  right-angles  to  the  rotating 
line,  the  two  lines  always  lying-  in  the  same  meridional 
plane.  There  are  three  planes  to  be  kept  in  mind:  (1) 
the  plane  of  rotation,  a  meridional  plane,  in  which  move 
both  the  rotating-  center  of  the  macula  and  the  visual 
axis,  the  plane  itself  being  fixed;  (2)  the  rotating-  plane, 
a  meridional  plane,  in  which  lie  the  center  of  the  macula 
and  the  two  fixed  points,  also  the  visual  axis  and  the 
axis  of  rotation;  (3)  the  rotating-  plane  which  contains 
only  the  two  fixed  points  and  the  line  connecting-  them 
— the  axis  of  the  rotation.  These  three  planes  are  at 
rig-ht-ang-les  to  each  other,  and  the  common  point  within 
the  eye  through  which  they  all  pass  is  the  center  of  ro- 
tation. The  planes  (1)  and  (2)  are  the  horizontal  and 
vertical  meridional  planes;  and  since  plane  (3)  cuts  the 
center  of  rotation  and  is  at  right-angles  to  planes  (1) 
and  (2),  it  can  be  none  other  than  the  equatorial  plane. 
Any  meridional  plane  may  be  a  plane  of  rotation;  but 
the  axes  of  oblique  rotations  will  be  studied  later  in  this 
chapter. 


22  THE    FUNDAMENTAL    PRINCIPLES 

The  correctness  of  what  has  been  taught  already  about 
ocular  rotations  may  be  made  clearer  by  a  study  of  Fig-. 
5,  which  is  a  modification  of  Fig.  1,  in  that  the  oblique 
diameters  have  been  omitted  and  the  curve  s-r  has  been 
added  to  represent  the  cornea.  A-B-D  represents  the 
concavity  in  the  anterior  part  of  the  orbital  fat  in  which 
the  eye  either  rests  or  moves.  The  globe  is  represented 
by  d-s-r-x-e-b.  The  center  of  the  concavity  and  that  of 
the  eye  is  c.  The  posterior  pole  is  at  b,  the  center  of  the 
macula.  The  true  anterior  pole  is  at  «,  but  for  conven- 
ience of  study  may  be  considered  as  at  r,  which  in  this 
figure  is  the  center  of  the  corneal  curve.  The  line  ex- 
tending from  b  to  r  is  the  antero-posterior  axis,  which, 
when  prolonged  into  space,  becomes  the  visual  axis.  In 
every  rotation  the  moving  point  is  b  and  the  moving  line 
is  b-r.  The  points  d  and  e  are  each  90°  from  b  and  lie 
on  the  horizontal  meridian.  The  line  d-e  is  a  diameter  and 
lies  in  the  same  plane  with  b-r  and  is  at  right-angles  to 
it.  In  Fig.  1  any  diameter  could  become  the  rotating 
line,  but  in  Fig.  5  the  only  diameter  that  can  be  the  ro- 
tating line  is  the  visual  axis  b-r.  Let  d-a-e-b  be  the  hor- 
izontal meridian  of  the  eye.  If  the  point  of  view  is  to  be 
changed  from  the  primary  position  to  a  point  in  space 
directly  below,  then  the  image  of  the  latter  point  must 
be  on  the  vertical  retinal  meridian  as  many  degrees  above 
the  center  of  the  macula  as  the  secondary  point  in  space  is 


OF    OCULAR   ROTATIONS. 


23 


Fig-  5- 


24  THE    FUNDAMENTAL,   PRINCIPLES 

below  the  first  point.  In  changing-  the  point  of  view,  the 
macula  will  move  upward  in  the  plane  of  the  vertical 
meridian  until  it  gets  beneath  the  second  image,  and  at 
the  same  time  the  visual  axis  will  rotate  on  the  point  c 
until  its  spacial  end  has  reached  the  second  point  of  view. 
In  this  rotation  d  and  e  have  not  moved  and  the  rotation 
has  been  around  d-e  as  an  axis.  In  this  rotation  the  only 
fixed  plane  has  been  the  plane  of  the  vertical  meridian, 
while  the  two  rotating  planes  have  been  the  plane  of 
the  horizontal  meridian  and  the  plane  of  the  equator. 
Throughout  the  rotation  these  three  planes  have  been  at 
right-angles,  each  to  the  other  two. 

THE  POSTERIOR  POLE. 

What  has  already  been  written  in  this  chapter  in  jus- 
tification of  the  selection  of  the  central  point  of  the  mac- 
ula as  the  posterior  pole  of  the  eye  should  be  enough 
to  convince  the  most  skeptical.  Truth  looked  at  from 
many  points  of  view  will  always  appear  as  truth;  error 
may  appear  to  be  the  truth  when  viewed  from  one  or  two 
standpoints,  but  it  is  sure  to  become  manifest  under  the 
clearer  light  of  many-sided  investigation.  Truth  is  al- 
ways simple,  and  the  greatest  truths  are  the  simplest. 
When  an  investigator  finds  himself  beset  with  difficulties, 
he  may  be  sure  that  error,  either  of  his  own  creating"  or 
that  has  been  handed  down  to  him,  shadows  his  path- 


OF    OCULAR   ROTATIONS.  25 

way.  Fundamental  errors,  until  discovered  and  discard- 
ed, are  dangerous  thing's,  for  out  of  these  come  many 
other  errors  of  greater  or  less  magnitude.  Helmholtz' 
fundamental  error  in  his  study  of  ocular  motions  was 
the  selection  of  the  center  of  the  cornea  as  the  anterior 
pole  of  all  eyes.  Because  of  this  fundamental  error,  he 
was  not  able  to  write  clearly  and  consistently  about  ocu- 
lar rotations.  He  must  have  recognized  the  murkiness  of 
his  own  teaching  on  this  subject  when  he  said  to  Her- 
man Knapp,  "Leave  this  chapter  aside,"  promising  "a 
different,  shorter,  and  more  comprehensive  presentation  " 
of  the  subject,  at  which  task  he  was  then  engaged.  This 
task  was  never  finished,  and  for  the  simple  reason  that 
he  was  never  able  to  rid  himself  of  the  fundamental  er- 
ror pointed  out  above,  though  he  lived  and  labored  for 
twenty-five  or  more  years  after  his  conversation  with 
Knapp.  With  the  consent  of  Arnold  Knapp,  the  well- 
known  son  of  Herman  Knapp,  the  author  reproduces  on 
page  26  a  part  of  a  letter  received  by  him  from  Dr. 
Knapp  soon  after  the  latter  had  read  his  smaller  book, 
"Ophthalmic  Neuro-Myology,"  which  had  just  come 
from  the  press  (1905),  a  companion  volume  to  "Ophthal- 
mic Myology." 

If  Helmholtz  had  grasped  the  truth  that  the  center  of 
the  macula  is  the  posterior  pole  of  every  eye,  his  funda- 
mental error  would  have  flown,  and  the  other  errors 


26 


THE   FUNDAMENTAL   PRINCIPLES 


ft. 


r*W1-. 


/f, 


OF    OCULAR    ROTATIONS.  27 

growing  out  of  it  would  have  been  supplanted  by  beau- 
tiful truths.  Then  his  chapter  on  ' '  movements  of  the 
eyes"  would  not  have  been  misty,  nor  would  Knapp 
have  complained  that  there  were  difficulties  in  this  chap- 
ter. 

In  further  refutation  of  Helmholtz'  erroneous  teach- 
ings which  have  been  perpetuated  in  all  books  on  the  eye, 
except  this  book  and  its  companion  volume,  "  Ophthalmic 
Neuro-Myology, "  it  will  be  profitable  to  study  Figs.  6, 
7,  and  8.  Fig.  6  represents  the  non-ideal  eye  of  Helm- 
holtz, in  which  o,  the  center  of  the  cornea,  is  the  ante- 
rior pole,  and  a,  between  the  macula  and  the  disc,  is  the 
posterior  pole,  and  o-c-a  is  the  optic  axis.  PP  is  the 
primary  point  of  view,  whose  retinal  image  is  at  m.  The 
so-called  "visual  axis"  of  Helmholtz,  connecting  object 
and  image,  crosses  the  optic  axis  at  the  nodal  point  N. 
SP  is  the  secondary  point  of  view,  whose  retinal  image, 
according  to  Helmholtz,  is  at  x.  The  indirect  visual 
line,  SP-x,  connecting  this  secondary  point  of  view  and 
its  image,  crosses  the  visual  axis  at  the  nodal  point  N. 
Motionless  objects  in  space  and  their  retinal  images  bear 
an  unalterable  relationship  to  each  other.  For  this  re- 
lationship to  be  maintained,  when  the  point  of  view  is 
changed,  the  visual  axis  must  assume  the  position  of  the 
indirect  visual  line  that  connected  the  secondary  point  of 
view  with  its  image  before  the  rotation  began.  Since 


28 


THE  FUNDAMENTAL  PRINCIPLES 


OF   OCULAR   ROTATIONS.  29 

in  Fig1.  6  the  visual  axis,  PP-m,  lies  to  the  outer  side  of 
the  center  of  rotation,  c,  while  the  indirect  visual  line, 
SP-x,  lies  to  the  inner  side  of  the  center  of  rotation,  c,  the 
former  can  never  be  made  to  assume  the  position  of  the 
latter.  To  show  the  confusion  that  would  occur  when 
such  an  eye  is  rotated,  the  figure  must  be  complicated 
by  drawing1  a  line  from  PP  through  c  to  n.  This  line, 
PP-c~n,  a  radius  of  retinal  curvature  prolonged,  will 
have  its  relationship  with  PP-m  unaltered  in  any  rota- 
tion of  the  eye.  When  the  eye  rotates  from  PP  to  the 
point  SP,  the  position  of  the  prolonged  radius  is  SP-n', 
and  that  of  the  visual  axis  SP-m '.  The  visual  axis  in 
space  has  reached  the  secondary  point  SP,  but  has  not 
reached  the  retinal  image  at  x,  for  even  SP-n  has 
stopped  short  of  x,  and  m  is  just  as  far  behind  n  as  ;«, 
in  the  primary  position,  was  distant  from  n.  The  mac- 
ula m  may  be  rotated  under  the  secondary  image  at  x\ 
but  when  this  is  done,  the  prolonged  radius  PP-n  will  as- 
sume the  position  ri'-c-e-r,  and  the  visual  axis  will  take 
the  direction  x-d-r.  Since,  in  monocular  vision,  any 
point  whose  image  is  on  the  macula  appears  to  lie  on  the 
visual  axis,  the  secondary  point  of  view  would  appear  to 
be  at  r  in  space,  removed  nearly  twice  as  far  from  the 
primary  point  as  it  was  before  the  rotation  began.  The 
images  have  remained  the  same  distance  apart,  but  the 
motionless  objects  in  space  have  apparently  become  more 


30  THE    FUNDAMENTAL,    PRINCIPLES 

widely  separated.     This  is  out  of  harmony  with  human 
experience. 

In  the  next  place,  study  the  ideal  eye  of  Helmholtz,  as 
shown  in  Fig-.  7.  In  this  figure  the  visual  axis  PP-m 
cuts  the  center  of  the  corneal  curve,  Helmholtz'  ante- 
rior pole,  and  therefore  coincides  with  his  optic  axis,  the 
macula  becoming-  the  posterior  pole.  The  secondary 
point  of  view  is  SP,  and  its  imag-e  is  supposed  to  be  at  x, 
the  two  being-  connected  by  the  indirect  visual  line 
SP-N-x.  As  in  Fig-.  6,  PP  and  SP  are  motionless 
points  in  space;  therefore  they  and  their  imag-es  must 
bear  a  fixed  relationship  the  one  with  the  others.  Hence, 
when  the  eye  rotates  from  one  point  of  view  to  the  other, 
the  visual  axis  PP-m  should  assume  the  position  of  SP-x; 
but  since  the  one  passes  throug-h  the  center  of  rotation 
and  the  other  does  not,  the  former  can  never  become  the 
latter.  To  show  what  would  take  place,  we  must  extend 
a  line  from  SP  throug-h  the  center  of  rotation,  c,  to  the 
retina  at  m'.  When  the  eye  is  rotated  from  PP  to  SP, 
the  visual  axis  PP-m  assumes  the  position  SP-ni '.  The 
spacial  end  of  the  visual  axis  has  reached  the  secondary 
point,  but  the  retinal  end  has  fallen  short  of  its  imag-e. 
The  macula,  m,  can  be  rotated  under  the  imag-e  at  x;  but 
when  this  has  been  done,  the  motionless  point  SP  will  ap- 
pear in  the  direction  x-c-d-r.  This,  too,  is  contrary  to 
all  experience. 


OF   OCULAR   ROTATIONS.  31 

Many  years  ago  the  author  announced  as  a  fact  that 
the  central  point  of  the  macula  is  the  posterior  pole,  and 
that  the  anterior  pole  may  or  may  not  be  the  center  of 
the  cornea.  He  also  announced,  at  the  same  time,  that  all 
lines  of  direction  are  radii  of  retinal  curvature  prolonged, 
and  not  axial  rays  of  light.  Fig.  8,  representing  a  non- 
ideal  eye — that  is,  an  eye  whose  true  anterior  pole  is  to 
the  nasal  side  of  the  center  of  the  corneal  curve — proves 
conclusively  that  he  discovered  the  truth.  In  this  figure 
PP  is  the  primary  point  of  view  and  SP  is  the  secondary 
point  of  view.  The  image  of  the  former  is  on  the  macula 
at  m,  while  the  image  of  the  latter  is  on  the  retina  at  m  . 
The  visual  axis  is  PP-m,  and  the  secondary  visual  line 
is  SPm '.  Since  these  lines  cross  each  other  at  the  center 
of  rotation  and  are  radii  of  retinal  curvature  prolonged, 
the  one  can  be  made  to  assume  the  position  of  the  other 
when  the  point  of  view  is  changed,  and  that,  too,  without 
disturbance,  either  apparent  or  real,  of  the  fixed  relation- 
ship of  the  two  motionless  points  in  space  and  their  re- 
spective retinal  images.  This  is  in  accord  with  human 
experience. 

Returning  to  the  ideal  eye,  shown  in  Fig.  7,  the  image 
of  SP  is  not  at  x,  but  at  m\  and  the  real  secondary  vis- 
ual line  is  SP-c-m  ,  whose  position  the  visual  axis  takes 
when  the  eye  rotates  from  the  primary  to  the  secondary 
point  of  view.  Thus  Fig.  7  may  be  made  to  teach  the 


32  THE   FUNDAMENTAL   PRINCIPLES 

truth,  after  erasing  the  continuous  line  SP-N-x  and  the 
dotted  line  d-r  to  the  left. 

In  Fig.  8  is  shown  Helmholtz'  so-called  "optic  axis" 
o-a,  and  on  it  his  nodal  point — "useless  each  e'en  with 
the  other."  The  sooner  they  are  forgotten,  the  better; 
and  the  angle  g"amma  should  be  included  in  the  forget- 
ting-. The  true  posterior  pole  is  the  central  point  of  the 
macula;  the  true  optic  axis  is  the  visual  axis;  and  the 
true  anterior  pole  is  that  point  of  the  cornea  cut  by  the 
visual  axis,  whether  it  be  the  center  of  the  cornea  or  not. 
An  undeniable  evidence  that  the  central  point  of  the 
macula  is  the  posterior  pole  is  the  fact  that  all  retinal 
meridians  cross  at  this  point — at  the  crossing1  of  the  me- 
ridians is  the  -pole.  There  is  no  longitude  there;  and, 
likewise,  there  is  no  latitude  for  adverse  argument. 

The  discovery  of  the  true  locations  of  the  posterior  and 
anterior  poles  of  the  eye  was  a  fortunate  one,  and  the  au- 
thor must  be  pardoned  for  feeling  some  joy  in  the  achieve- 
ment. On  this  discovery  is  based  the  law  of  monocular 
and  binocular  rest  and  motion,  and  the  law  of  direction. 

Before  passing  to  the  study  of  binocular  rotation,  it  may 
be  profitable  to  the  reader  to  review  in  parallel  columns 
the  conflicting  teachings  of  Helmholtz  and  the  author. 


HEI,MHOI/rz. 

(1)  The  center  of  the   cornea   is 
always  the  anterior  pole,   and   the 


THE  AUTHOR. 

(1)  The  center  of  the  macula   is 
always  the  posterior  pole,  and  the 


OF    OCULAR    ROTATIONS. 


33 


center   of    the    macula    is  the  pos- 
terior pole  only  in  ideal  eyes. 

(2)  The  optic  axis  begins  always 
at  the  central  point  of   the  cornea, 
passes  backward  through  the  center 
of  rotation  to  the  retina,  rarely  at 
the  central  point  of  the  macula,  but 
usually  to  a  point  between  the  mac- 
ula and  the  optic  disc. 

(3)  The  optic   axis  is  the  visual 
axis  only  in  the  ideal  eye,  and  only 
then  does  the  visual  axis  cut  the 
center    of    rotation.      Usually    the 
visual  axis  misses  the  center  of  ro- 
tation by  passing  to  the  outer  side 
of  it,  crossing  the  optic  axis  at  the 
nodal  point,  and  lying  in  only  one 
meridional  plane. 

(4)  Visual  lines  are  axial  rays   of 
cones  of  light,  as  is  also  the  visual 
axis,  and  all  these  cross  the  optic 
axis  at  the  nodal   point.     Even   in 
ideal  eyes  the  visual  lines  do  not 
cross  the  visual  axis  at  the  center  of 
rotation. 

(5)  In  passing  from  one  point  of 
view  to    any  other,  the  visual  axis 
of  a  non-ideal  eye  cannot  move  in 
a  plane  of  a  meridian  except  when 
the  rotation  is  directly  to  the  right 
or  left. 

(6)  In  cardinal  and  oblique  rota- 


center  of  the  cornea  is  the  anterior 
pole  only  in  ideal  eyes. 

(2)  The  optic  axis  always  begins 
at  the  center  of  the  macula,  passes 
through  the  center  of  rotation  and 
cuts  the  cornea,  rarely  at  its  center, 
but  usually  to  the  nasal  side. 


(3)  The  optic  axis  in  all  eyes  is 
the  visual  axis  and  is  the  line  of 
intersection  of  all  meridional  planes, 
hence  it  lies  in  the  plane  of  every 
meridian. 


(4)  Visual  lines  are  not  axial  rays 
of    light,    but   are    radii   of   retinal 
curvature   prolonged,    all    of    them 
crossing  the  visual  axis  at  the  center 
of  rotation,  which  is  the  center  of 
retinal  curvature. 

(5)  In   monocular  motion   every 
rotation  plane  is  a  meridional  plane 
extended,  and  the  visual  axis  always 
moves  in  this  plane. 


(6)  The   axis  of   every    rotation, 


34 


THE    FUNDAMENTAL    PRINCIPLES 


tions  starting  from  the  primary  point 
of  view  or  returning  to  it,  the  axis 
of  any  rotation  lies  in  Listing's 
plane;  the  axis  of  rotation  from  one 
secondary  point  to  another  second- 
ary point  lies  in  a  plane  bisecting 
the  angle  between  Listing's  plane 
and  the  equatorial  plane. 

(7)  The  object  in   space  and  its 
retinal   image   are   connected   by   a 
straight  line  which  crosses  all  simi- 
lar lines  at  the  nodal  point,    and 
never  at  the  center  of  rotation. 

(8)  Thespacial  pole,  if  on  the  same 
straight  line  with  the  two  poles  of 
the  eye,  cannot  be  the  direct  point 
of  view  for  non-ideal  eyes. 


whether  cardinal  or  oblique,  whether 
from  a  primary  to  secondary  point  of 
view,  or  vice  versa,  or  whether  from 
one  secondary  to  another  secondaiy 
point  of  view,  lies  in  the  equatorial 
plane. 


(7)  The  object  in   space  and  its 
retinal  image  are  always  connected 
by  a  straight  line  which  crosses  all 
similar  lines  at  the  center  of  rota- 
tion and  at  no  other  point. 

(8)  The  spacial  pole  is  on  the  same 
straight  line  with  the  two  poles  of 
the  eye  and   is  the  direct  point  of 
view  for  all  eyes. 

In  drawing-  the  above  parallel,  no  attempt  has  been 
made  to  quote  the  exact  language  of  Helmholtz,  or  any 
of  his  followers,  on  either  of  the  eight  points  of  difference; 
but  that  he  has  been  fairly  represented  as  to  his  teach- 
ings, no  one  will  deny.  His  two  fundamental  errors  were: 
(1)  In  not  taking  the  central  point  of  the  macula  for  his 
posterior  pole,  and  (2)  in  his  axial-ray  theory  of  direction. 
To  be  in  agreement  on  the  location  of  the  posterior  pole 
and  on  the  law  of  direction  would  mean  agreement  every- 
where. If  on  these  points  Helmholtz  is  right,  the  au- 
thor is  wrong;  if  the  author  is  right  on  these  points,  then 
Helmholtz  is  wrong.  The  teaching  of  the  one  who  is 


OF    OCULAR    ROTATIONS.  35 

correct  in  the  location  of  the  posterior  pole  and  in  his  con- 
ception of  the  law  of  direction  will  stand. 

LINES  OF  DIRECTION. 

One  of  these  times  some  one  will  read  this  language 
in  Le  Conte's  book  on  "Sight:"  "For  every  retinal 
point  there  is  a  corresponding  spacial  point;"  and  "the 
rods  and  cones  see  end-on."  Having  read  it,  he  will  be 
ready  to  claim  that  Le  Conte  was  first  to  discover  the 
true  law  of  direction;  for  the  first  quotation  would  mean 
that  the  retinal  and  spacial  curves  are  concentric  and 
that  lines  connecting  the  corresponding  points  would  cut 
this  common  center;  and  the  second  quotation  would 
mean  the  same  thing,  for  do  not  rods  and  cones  all  point 
toward  the  center  of  the  retinal  curve?  In  a  letter  to 
the  author,  in  reply  to  one  he  had  written  him,  Le  Conte 
said  that  he  had  used  the  language  quoted  above  only  in 
a  rough  sense,  for  he  certainly  believed  that  Helmholtz' 
axial-ray  theory  of  direction  was  correct,  and  that  all 
lines  of  direction  cross  at  the  nodal  point.  In  his  first 
edition  of  "  Sight,"  his  figure  representing  the  horopter 
shows  the  lines  of  direction  crossing  each  other  at  the 
nodal  point,  while  the  horopteric  curve  cuts  the  centers 
of  rotation.  Fig.  9  is  an  exact  copy  from  his  book  (first 
edition,  1882).  In  his  second  edition  of  "Sight,"  the 
figure  representing  the  horopter  has  been  changed,  but 


36 


THE  FUNDAMENTAL  PRINCIPLES 


not  in  respect  of  the  point  of  crossing  of  the  visual  lines, 
for  these  are  made  to  cross  at  the  nodal  point.  The 
change,  as  shown  in  Fig.  10,  reproduced  from  the  second 
edition  of  "Sight"  (1898),  is  shown  in  the  horopteric 
circle  which  has  been  constructed  through  the  two  nodal 


Fig.  9. 


points  and  the  point  of  fixation;  whereas,  in  the  first 
edition,  the  same  circle  had  been  constructed  through 
the  two  centers  of  rotation  and  the  point  of  fixation. 
L/e  Conte  had  written  the  author  that  one  result  of  our 


OF    OCULAR    ROTATIONS. 


37 


correspondence  would  be  a  change  in  the  construction  of 
the  horopter  in  the  second  edition  of  his  book. 

Extracts  from  some  of  Le  Conte's  letters  are  photo- 
graphically reproduced  on  page  38  and  will  be  interesting- 


Fig.  10. 

reading1  in  this  connection.  What  he  denies  so  emphat- 
ically in  the  reproduced  letter  is  that  the  lines  of  di- 
rection cross  at  the  center  of  retinal  curvature. 

The   fig-ure    referred   to   in    the   seventh   line    of  the 


38  THE    FUNDAMENTAL   PRINCIPLES 

'V***-**'- 


OF    OCULAR    ROTATIONS.  39 

Le  Conte  letter  was  on  page  80  of  the  author's  "New 
Truths  in  Ophthalmology "  (first  edition).  The  thing 
represented  in  that  figure,  and  declared  not  true,  is  the 
crossing  of  the  visual  lines  at  the  center  of  retinal  curva- 
ture— the  center  of  rotation — for  this  was  the  one  truth 
taught  by  that  illustration. 

The  reproduced  figures  of  the  horopter  will  be  re- 
ferred to  again  in  the  discussion  of  that  subject  fur- 
ther on. 

Monocular  rotation  differs  enough  from  binocular  ro- 
tation to  justify  the  study  of  each  separately.  The 
same  muscles  are  concerned  in  each,  but  the  innervations 
are  not  identical  throughout.  The  volitional  brain  cen- 
ters, with  one  exception,  are  alike  concerned  in  each,  but 
with  monocular  rotations  the  fusion  centers  have  nothing 
to  do.  In  the  study  of  monocular  rotation  one  eye  must 
be  considered  as  not  existing,  as  blind,  or  as  obscured. 
It  has  been  shown  conclusively  that  the  spacial  pole  of 
one  eye  is  the  direct  point  of  view  for  that  eye,  and  that 
the  image  of  that  point  of  view  is  on  the  center  of  the 
macula,  which  is  the  posterior  pole  of  the  eye.  It  has 
also  been  shown  that  every  secondary  point  of  view  in 
the  field  of  vision  must  lie  on  some  one  spacial  meridian; 
if  not  on  the  vertical  meridian,  then  either  to  the  right 
or  to  the  left  of  it;  and  if  not  on  the  horizontal  meridian, 
then  either  above  or  below  it.  The  image  of  every  sec- 


40  THE    FUNDAMENTAL    PRINCIPLES 

ondary  point  of  view  must  lie  on  a  corresponding*  retinal 
meridian;  but  if  the  object  be  above  the  horizontal  spa- 
cial  meridian,  its  image  must  be  below  the  horizontal  ret- 
inal meridian,  and  vice  versa',  if  the  object  be  to  the  right 
of  the  vertical  spacial  meridian,  its  image  must  be  to  the 
left  of  the  vertical  retinal  meridian,  and  vice  versa.  The 
secondary  object  and  its  image  bear  the  same  relationship, 
in  degrees,  to  the  primary  object  and  its  image,  and  vis- 
ual lines  connecting  them  cross  each  other  at  the  center  of 
rotation.  The  purpose  of  any  rotation  is  to  make  the  di- 
rect line  of  vision,  the  visual  axis,  take  the  place  of  an 
indirect  line  of  vision.  To  do  this,  the  spacial  pole,  which 
is  the  point  of  crossing  of  all  spacial  meridians,  must  move 
along  that  spacial  meridian  on  which  lies  the  second 
point  of  view,  until  it  reaches  that  point;  and  the  center 
of  the  macula,  which  is  the  point  of  crossing  of  all  retinal 
meridians,  must  move,  in  the  direction  opposite  to  the  mo- 
tion of  the  spacial  pole,  along  that  retinal  meridian  on 
which  lies  the  image  of  the  second  point  of  view,  until  it 
gets  under  that  image.  The  visual  axis  is  thus  rotated 
in  the  plane  of  that  retino-spacial  meridian  on  which  are 
lying  the  two  spacial  points  and  their  respective  retinal 
images. 

To  effect  all  possible  monocular  rotations,  the  four 
straight  muscles  and  the  two  obliques  are  essential.  A 
single  muscle  can  effect  a  given  rotation  only  when  that 


OF   OCULAR  ROTATIONS.  41 

muscle  is  bisected  by  the  rotation  plane  (always  a  merid- 
ional plane)  from  its  origin  to  its  insertion.  If  two  mus- 
cles, one  of  which  is  always  an  oblique  muscle,  are  re- 
quired to  effect  a  cardinal  rotation,  the  resultant  action 
of  these  two  muscles  would  be  the  same  as  the  action  of 
one  imaginary  straight  muscle  which  would  be  bisected 
from  origin  to  insertion  by  the  real  plane  of  rotation.  If 
three  muscles  are  required  for  any  oblique  rotation  (more 
than  three  muscles  are  never  active  in  any  rotation),  the 
resultant  action  of  these  three,  one  of  which  is  an  oblique 
muscle,  is  not  the  same  as  would  be  effected  by  a  single 
imaginary  muscle  which  would  be  bisected  throughout 
its  length  by  the  rotation  plane.  As  will  be  shown  later, 
oblique  rotations  are  not  effected  around  a  fixed  single 
axis  at  right-angles  to  the  rotation  plane,  but  around 
two  moving  axes  at  right-angles  to  each  other  and  to  the 
visual  axis,  thus  insuring  against  that  torsion  which 
would  result  if  such  rotation  were  around  a  single  fixed 
axis. 

If  there  were  only  as  many  rotation  planes  as  there  are 
minutes  on  one-half  of  the  equator  of  the  eye,  and  two  in- 
dividual muscles  existed  for  every  rotation  plane,  there 
would  have  to  be  twenty-one  thousand  and  six  hundred 
muscles,  and  an  equal  number  of  voluntary  innervation 
centers,  for  effecting  all  possible  monocular  rotations, 
each  around  a  fixed  axis.  In  the  wonderful  mechanism  of 


42  THE   FUNDAMENTAL   PRINCIPLES 

monocular  motions  only  six  muscles  are  needed,  the  four 
straight  muscles  and  the  two  obliques,  and  only  eight 
voluntary  centers  are  requisite,  one  center  for  each 
straight  muscle  and  two  for  each  oblique  muscle.  Only 
one  muscle  and  one  innervation  center  are  needed  for  a 
cardinal  motion  either  toward  the  temple  or  toward  the 
nose,  provided  the  lateral  recti  are  bisected  by  the  plane 
of  the  horizontal  retinal  meridian.  Two  muscles  and 
two  innervation  centers  are  necessary  if  the  visual  axis 
is  to  be  rotated  in  the  plane  of  the  vertical  meridian.  If 
the  visual  axis  is  to  be  rotated  in  the  plane  of  any  oblique 
meridian,  this  must  be  done  by  the  simultaneous  and 
harmonious  action  of  three  muscles  under  impulses 
from  three  volitional  brain  centers.  One  of  the  three 
muscles,  an  oblique,  will  prevent  any  rotation  on  the  vis- 
ual axis  while  it  is  being  rotated  in  the  rotation  plane 
by  the  other  two  muscles  (recti),  around  two  moving 
axes,  these  axes  being  always  the  transverse  and  verti- 
cal axes  of  the  eye.  That  the  prime  object  of  the  ob- 
lique muscles  is  to  prevent  torsioning  in  vertical  and 
oblique  rotations,  regardless  of  whether  it  helps  or  hin- 
ders a  rectus  muscle  in  effecting  its  rotation  around  the 
transverse  or  vertical  axis  of  the  eye,  is  shown  by  the  fact 
that,  if  the  rotation  of  the  right  eye  is  up  and  to  the 
right,  the  superior  oblique  acts  with  the  superior  and  ex- 
ternal recti,  hindering  the  former,  but  helping  the  latter. 


OF    OCULAR   ROTATIONS.  43 

The  same  rotation  of  the  left  eye  would  be  effected  by 
the  inferior  oblique  acting1  with  the  superior  and  internal 
recti,  helping-  the  former,  but  hindering  the  latter.  In 
either  case  the  oblique,  by  preventing-  rotation  on  the 
visual  axis,  enables  the  superior  rectus  to  rotate  the  eye 
on  the  transverse  axis  as  if  it  were  going  straight  up, 
and  at  the  same  time  enables  the  externus  of  the  right 
eye,  or  the  internus  of  the  left,  to  rotate  the  eye  on  the 
vertical  axis,  as  if  the  eye  were  being-  turned  directly  to 
the  right.  These  three  forces  combined  (not  converted 
into  one  force  in  the  sense  of  creating  a  fixed  axis  at 
right-angles  to  the  plane  of  rotation)  rotate  the  eye  in 
an  oblique  plane  without  torsioning,  just  as  if  the  eye 
had  been  rotated  first  on  the  vertical  axis  to  a  point  in 
the  horizontal  plane  directly  beneath  the  secondary 
point,  and  thence  directly  up  around  the  transverse  axis 
of  the  eye  to  that  point. 

Listing's  law  was  quoted  correctly  in  the  first  edition 
of  this  book  as  follows:  "When  the  line  of  fixation 
passes  from  its  -primary  to  any  other  position,  the  angle 
of  torsion  of  the  eye  in  this  second  position  is  the  same  as 
if  the  eye  had  arrived  at  this  second  position  by  turning- 
about  a  fixed  axis  perpendicular  to  the  first  and  second 
positions  of  the  line  of  fixation. ' '  Immediately  following 
this  quotation  the  author  said:  "Certainly  it  is  around 
such  an  axis  [but  it  isn't]  that  the  eye  rotates  from  the 


44 


THE  FUNDAMENTAL  PRINCIPLES 


primary  point  of  view  to  the  obliquely  placed  secondary 
point  of  view.  It  is  equally  certain  that  there  would  be 
a  torsioning  unless  a  preventive  force  were  called  into 
action."  The  obliques  were  given  the  credit  for  the  force 
that  prevents  torsioning  in  both  vertical  and  oblique 
rotations.  To  the  obliques  belong"  this  power,  and 
without  them  the  torsioning  would  be  inevitable  in  ob- 
lique rotations,  even  around  two  axes. 


J. 

Fig.   ii. 

In  oblique  rotations  the  oblique  muscles  make  impossi- 
ble the  existence  of  a  fixed  axis  of  rotation  at  right- 
angles  to  the  rotation  plane.  There  are  only  two  axes  of 
rotation,  around  one  or  both  of  which  every  possible  oc- 
ular motion  takes  place.  These  axes  are  fixed  and  at 
right-angles  to  the  rotation  plane  only  when  the  rota- 
tions are  in  the  four  cardinal  directions,  and  then  the 
motion  is  around  only  one  axis.  There  is  no  torsion  in 


OF  OCULAR   ROTATIONS.  45 

such  a  cardinal  rotation.  In  Fig-.  11  these  two  axes  are 
shown.  The  circle  a-d-b-e  represents  the  equator  of  the 
eye,  the  line  a-b  is  the  vertical  axis,  and  the  line  d-e  is 
the  transverse  or  horizontal  axis  of  the  eye.  These  are 
at  right-angles  to  each  other,  the  one  in  the  plane  of  the 
vertical  meridian  and  the  other  in  the  plane  of  the  hori- 
zontal meridian,  and  both  lie  in  the  plane  of  the  equa- 
tor. They  are  both  at  right-angles  to  the  visual  axis. 
Around  a-b  the  visual  axis  rotates  directly  to  the  right 
or  left  and  without  torsion.  Around  d-e  the  visual  axis 
moves  directly  up  or  down  and  without  torsion.  These 
cardinal  rotations  can  be  shown  easily  by  means  of  a 
rubber  ball  to  represent  the  eye,  and  two  knitting  nee- 
dles, one  to  represent  the  visual  axis  and  the  other  to  rep- 
resent one  or  the  other  of  these  two  axes  of  rotation.  The 
rubber  ball  and  the  knitting-  needles  are  worthless  in  the 
study  of  oblique  rotations,  for  the  reason  that  there  can 
be  no  fixed  axis  for  any  one  of  these  rotations.  Any  and 
every  oblique  rotation  is  around  both  the  vertical  and  the 
horizontal  axes,  a-b  and  d-e,  which  are  always  at  right- 
angles  to  the  visual  axis,  but  not  at  right -angles 
to  any  oblique  rotation  plane.  These  axes  are  not 
fixed,  but  are  themselves  in  motion  as  the  eye  rotates 
around  them  in  any  oblique  plane.  As  in  cardinal  rota- 
tions, so  in  oblique  rotations,  the  rotation  plane  is  a  fixed 
plane.  The  duty  of  each  of  the  three  muscles  concerned 
in  an  oblique  rotation  is  well  defined,  and  each  does  its 


46  THE   FUNDAMENTAL,   PRINCIPLES 

duty  well  in  the  interest  of  correct  orientation.  The 
oblique  muscle  prevents  the  loss  of  parallelism  of  the 
vertical  axis  of  the  eye  with  the  median  plane  of  the 
head.  The  superior  rectus  elevates  the  eye  by  rotating 
it  on  the  transverse  axis,  d-e\  while  the  external  rectus, 
acting-  simultaneously  and  harmoniously  with  the  other 
two  muscles,  rotates  the  eye  to  the  rig-fat  around  the 
vertical  axis,  a-b.  As  these  two  rotations  beg-in,  the  axis 
of  each  is  made  to  move  by  the  power  that  is  making  the 
eye  rotate  around  the  other,  hence  they  cannot  be  fixed 
axes.  At  the  end  of  such  an  oblique  rotation  (up  and  to 
the  right),  there  is  no  more  torsion  than  if  the  eye  had 
been  first  rotated  outward  on  the  fixed  axis  a-b,  and  then 
directly  upward  on  the  fixed  axis  d-e.  In  every  possible 
monocular  rotation  the  vertical  axis  of  the  eye  must  be 
kept  parallel  with  the  median  plane  of  the  head,  and  this 
is  the  task  that  is  set  for  the  oblique  muscles. 

The  study  of  torsion  in  oblique  rotations  on  a  fixed 
axis,  at  right-angles  to  the  rotation  plane,  as  it  appeared 
in  the  first  edition,  is  reproduced  in  the  four  following 
pag-es  as  matter  of  mathematical  interest,  but  not  as  a 
physiolog-ical  truth. 

The  accompanying'  cut,  Fig.  12,  was  designed  by  Mad- 
dox  for  solving  "false  torsion."  It  is  taken  from  his 
very  interesting  book  on  "The  Ocular  Muscles,"  pub- 
lished in  1898.  The  following  is  the  solution  in  his  own 
words: 


OF    OCULAR    MOTIONS. 


47 


Fig.   12. 

4  'Taking  VC  as  unity  - 

Since  OV  =  sin  I 

and  2£  =  cosR, 

.-.     OM  =  sinIcosR. 
Moreover    OC  =  cos  I; 


OM  =  sin  i  cos  R  =  tan  I  cos  R. 

OC  cos  I 


But  ^  =  tan(I  —  X); 

.  '.  tan  (I—  X)  =  tan  I  cos  R. 

Or  X  =  I—  tan"1  (tan  I  cos  R) 

"Putting    this    into    language:    The    false   torsion    is 
equal  to  the  angle  from  the  vertical,  or  from  the  hori- 


48  THE    FUNDAMENTAL    PRINCIPLES 

zontal,  of  the  axis  about  which  the  eye  rotates,  less  the 
angle  whose  tangent  is  the  multiple  of  the  tangent  of 
the  inclination  of  the  axis  of  motion  with  the  cosine  of 
the  angle  traversed  by  the  line  of  fixation. 

"The  short  table  overleaf  will  give  an  idea  of  the 
amount  of  false  torsion  which  takes  place  on  looking  in 
any  diagonal  direction  midway  between  any  two  of  the 
cardinal  directions. 

"Since  the  greatest  false  torsion  of  which  the  eye  is 
capable  occurs  at  the  extremity  of  these  diagonals,  we 
may  see  at  once  that  it  does  not  ever  much  exceed  10°." 

Rotation  about  an  axis  45°  from  the  Jiorizontal. 


Degrees    |  5° 

10° 

15°  |  20° 

25° 

80° 

35° 

40° 

4o° 

Torsion    |  6^' 

26' 

1°  |1°  47' 

2°  49' 

4°  6' 

5°  40' 

7°33/ 

9°  44' 

The  above  table  was  taken  from  Maddox. 

At  the  author's  request,  Prof.  John  Daniel,  of  Van- 
derbilt  University,  designed  Fig.  13  with  the  view  of 
determining  the  amount  of  torsion  that  would  occur  as 
the  result  of  oblique  rotation  of  the  eyes,  if  it  were  not 
prevented  by  the  oblique  muscles.  The  following  is  the 
solution  by  Professor  Daniel: 


OF    OCUIvAR    MOTIONS. 


49 


Fig-  i3- 
Make          vo  =  unity. 

I  =  angle  between   the  vertical  and  the 

axis  of  rotation, 
=  ocv. 
R  =  angle  through  which  the  eye  is  turned 

on  said  axis, 
—  vot. 
Then  X  =  angle  of  torsion,  vcm. 

R       \  rfnr  in  thpfrian{r1p7y/->«  wphavp 
ot2!/     sinX  -±vm  =  sinoz'c-^-  me). 


COS  I  vers  R 


cos2R-|-c 
•       "XT*  *  vin  •       /c\r\o       T\  "vnt 

sin  X.  =  sin  ovc  —  =  sin  (90  — I)  —c 

cos  I  vers  R      cos  I  vers  R 


' cos»  R+  cot2  I 


=  sn 


m~V      c°s  *  v^  R       \ 
\  i/  cos*  R+  cot2 1  / 


50 


THE  FUNDAMENTAL  PRINCIPLES 


"  That  is,  starting  from  a  primary  position,  when  the 
eye  is  rotated  R  degrees  on  axis  inclined  I  degrees  to  the 
vertical  (or  horizontal)  the  resulting  torsion,  X,  is  an 
angle  whose  sine  is  equal  to  cos  I  times  the  vers  R,  di- 
vided by  the  square  root  of  the  sum  of  the  squares  of 
cos  R  and  cos  I.  The  numerical  value  of  the  torsion,  X, 
when  the  inclination  of  the  axis  is  45°,  is  as  follows  for 
angles  of  rotation,  R,  as  follows: 


Angle  of  rotation  = 
R— 

5° 

10° 

16° 

20° 

25° 

30° 

35° 

40° 

45° 

Torsion         

fi'4' 

•?6' 

1° 

1°47' 

2°49' 

4°6' 

5°40' 

7°33' 

9°44' 

"  This  was  worked  out  independently  of  the  simpler 
formula  given  in  Maddox,  but  the  two  are  equivalent." 

The  mistake  made  by  Maddox  was  in  supposing  that 
no  effort  was  made  by  the  obliques  to  correct  the  tor- 
sioning  that  otherwise  would  occur. 

The  work  of  mastering  the  study  of  ocular  rotations  is 
greatly  simplified  by  a  knowledge  of  the  fact  that  a  car- 
dinal rotation  is  around  one  of  two  axes,  and  that  oblique 
rotations  are  around  both  these  axes  simultaneously,  and 
that  no  other  axes  are  possible.  Rotation  planes  are  in- 
numerable, but  the  axes  of  rotations  are  only  two,  the 
vertical  and  the  transverse  axes  of  the  eyes.  Although 
every  vertical  motion  is  effected  by  two  muscles,  and 
every  oblique  rotation  by  three  muscles,  nevertheless  it 
will  be  profitable  to  study  each  muscle  and  its  plane. 


OF  OCULAR  ROTATIONS.  51 

THE  INDIVIDUAL  MUSCLE  AND  ITS  PLANE  OF 
ROTATION. 

If  the  nine  conjugate  innervations  were  never  defective, 
and  if  there  were  no  such  thing  as  heterophoria,  there 
would  be  but  little  need  for  studying  the  ocular  muscles 
as  to  their  separate  action  or  in  the  light  of  synergism 
and  antagonism.  In  paralysis  and  paresis  of  an  ocular 
muscle,  a  diagnosis  can  be  made  easily  and  quickly  only 
when  one  knows  what  would  be  the  result  of  unopposed 
action  of  the  affected  muscle. 

The  reader  is  supposed  to  be  fully  acquainted  with  the 
extrinsic  ocular  muscles,  as  to  their  origin,  course,  inser- 
tion, and  nerve  supply.  With  this  knowledge  already  ac- 
quired it  is  easy  to  pass  to  the  study  of  the  result  or  re- 
sults of  the  contraction  of  any  single  muscle.  The  axis 
of  rotation  of  the  eye  by  any  one  muscle  must  be  at  right- 
angles  to  the  plane  of  rotation  for  this  muscle.  This  plane 
must  bisect  the  muscle  at  its  origin  and  at  its  attachment, 
and  must  also  pass  through  the  center  of  rotation  of  the 
eye.  As  to  the  internus  or  externus,  the  relationship 
that  the  muscle  plane  bears  to  the  horizontal  plane  of  the 
eye  indicates  the  exact  rotation  that  will  result  from  its 
action.  If  the  rotation  plane  of  the  internus  coincides 
with  the  horizontal  plane  of  the  eye,  then  this  muscle 
will  have  only  one  result  from  its  contraction;  that  is, 


52  THE    FUNDAMENTAL    PRINCIPLES 

the  eye  will  be  turned  directly  in  (ad version),  the  rota- 
tion taking-  place  around  the  vertical  axis  of  the  eye. 
This  action  of  the  internus  may  be  termed  its  principal 
action;  and  under  such  condition  there  can  be  no  subor- 
dinate action  of  the  muscle.  Some  may  prefer  the  terms 
used  by  Dr.  Maddox,  viz.,  pre-eminent  and  subsidiary 
action. 

If  the  plane  of  rotation  of  the  internus  does  not  coin- 
cide with  the  horizontal  plane  of  the  eye,  the  simple  ro- 
tation is  impossible.  Let  this  muscle  plane  be  inclined 
down  and  out,  as  it  must  be  when  the  internus  is  attached 
too  high,  then  the  axis  of  rotation  cannot  be  the  vertical 
axis  of  the  eye,  for  the  former  must  bear  the  same  rela- 
tionship to  the  latter  that  the  muscle  plane  bears  to  the 
horizontal  plane  of  the  eye.  The  unopposed  action  of 
this  muscle  cannot  rotate  the  eye  directly  in,  but  associ- 
ated with  the  adversion  there  will  be  superversion  and  in- 
ward torsion  or  declination,  both  of  which  are  subordi- 
nate actions.  Let  the  internus  be  attached  too  low  on 
the  globe,  then  its  plane  of  rotation  will  have  an  inclina- 
tion down  and  in,  forming-  a  definite  angle  with  the  hor- 
izontal plane  of  the  eye.  The  axis  of  rotation  will  form 
the  same  angle  with  the  vertical  axis  of  the  eye.  Unop- 
posed, the  internus  thus  attached  cannot  rotate  the  eye 
directly  inward,  but,  associated  with  the  adversion  (prin- 
cipal), there  will  be  sub-version  and  an  outward  torsion 


OF    OCULAR    ROTATIONS.  53 

or  declination.  It  is  reasonable  to  suppose  that  the  plane 
of  rotation  of  the  internus  does  not  always  coincide  with 
the  horizontal  plane  of  the  eye.  Thus  H  is  shown  that, 
by  error  of  attachment  (too  high  or  too  low),  an  internus 
may  be  one  factor  in  a  hyperphoria  or  a  cataphoria,  and 
in  a  minus  or  a  plus  cyclophoria. 

In  like  manner  rotation  by  the  external  rectus  muscle 
may  be  studied.  If  the  plane  bisecting  the  origin  and  in- 
sertion of  this  muscle,  and  passing  throug~h  the  center  of 
rotation,  coincides  with  the  horizontal  plane  of  the  eye, 
its  action  will  result  in  abversion  (principal,  without  any 
kind  of  subordinate,  action).  If  the  muscle  be  attached 
too  high,  its  plane  of  rotation  must  be  inclined  down  and 
in,  its  axis  of  rotation  making  the  same  angle  with  the 
vertical  axis  that  its  plane  makes  with  the  horizontal 
plane.  The  action  of  the  externus  thus  attached  will 
have  a  triple  result:  (a)  abversion  (principal);  (Z>)  super- 
version  (subordinate);  and  (c)  an  outward  torsion  or  dec- 
lination (subordinate). 

If  the  externus  be  attached  too  low,  its  plane  of  rota- 
tion will  be  tilted  down  and  out,  forming  a  definite  angle 
with  the  horizontal  plane,  and  its  axis  of  rotation  will 
form  an  equal  angle  with  the  vertical  axis.  In  contract- 
ing, the  eye  will  be  abverted  (principal  action);  it  will 
also  be  sub-verted,  and  there  will  be  an  inward  torsion 
(subordinate  actions).  Thus  it  is  shown  that  an  externus 


54  THE   FUNDAMENTAL,   PRINCIPLES 

attached  too  high  or  too  low  will  be  one  factor  in  the  pro- 
duction of  a  hyperphoria  or  a  cataphoria,  and  just  as  cer- 
tainly a  factor  in  the  production  of  a  plus  or  a  minus 
cyclophoria. 

It  will  be  observed,  from  the  foregoing,  that  either  an 
internus  or  an  externus  attached  in  greater  part  above 
the  horizontal  plane,  will  have  the  superverting  effect  of 
a  superior  rectus;  and  that  either  muscle  attached  in 
greater  part  below  the  horizontal  plane  of  the  eye,  will 
have  the  sub-verting  effect  of  the  inferior  rectus.  The 
torsioning  effect  of  an  internus  attached  too  high  will  be 
in,  while  that  of  an  externus  with  a  too  high  attachment 
will  be  out.  An  internus  attached  too  low  will  produce 
a  plus  cyclophoria,  while  an  externus  attached  too  low 
will  cause  a  minus  cyclophoria.  Thus  it  will  be  seen  that 
an  internus  will  have  the  same  kind  of  verting  and  tor- 
sioning effects  as  the  superior  or  inferior  rectus  towards 
which  its  attachment  is  displaced.  The  external  rectus 
will  have  the  superverting  or  sub-verting  effect  of  the  su- 
perior or  inferior  rectus  towards  which  its  attachment  is 
displaced,  but  the  opposite  torsioning  effect.  The  prac- 
tical nature  of  these  observations  will  be  shown  in  the 
study  of  operations  on  the  lateral  recti  muscles. 

The  correctness  of  what  has  been  said  about  the  action 
of  the  internus  or  externus,  when  the  plane  of  rotation 
does  not  coincide  with  the  horizontal  plane  of  the  eye,  can 


OF    OCULAR    ROTATIONS.  55 

be  easily  demonstrated  by  the  use  of  the  rubber  ball  and 
the  knitting  needles,  and  in  the  same  way  can  be  studied 
the  individual  action  of  the  superior  and  inferior  recti 
and  that  of  the  obliques.  The  rotation  plane  of  an  indi- 
vidual muscle  bisects  the  muscle  and  cuts  the  center  of 
rotation.  Only  in  properly  attached  lateral  recti  mus- 
cles does  this  plane  correspond  with  a  meridional  plane, 
hence  the  axes  of  rotations  by  the  other  four  muscles  can- 
not lie  in  the  equatorial  plane. 

The  origin,  course,  and  insertion  of  the  superior  rectus, 
also  of  the  inferior  rectus,  make  it  impossible  for  the 
plane  of  rotation  for  either  one  of  these  muscles  to  coin- 
cide with  the  vertical  antero-posterior  plane  of  the  eye 
when  in  the  primary  position.  The  plane  of  rotation  for 
either  one  of  these  muscles  is  made  to  pass  through  the 
center  of  the  origin  of  the  muscle,  the  center  of  rotation 
of  the  eye,  and  the  center  of  the  insertion  of  the  muscle. 
It  is  only  when  either  muscle  has  a  very  definite  attach- 
ment that  its  plane  of  rotation  can  be  vertical.  A  dis- 
placement in  or  out  of  the  attachment  of  either  the 
superior  or  the  inferior  rectus  will  not  change  the  kind 
of  rotation  to  be  effected,  but  it  would  modify  the  ex- 
tent of  the  three  effects  of  its  contraction.  For  sim- 
plicity of  study,  it  may  be  considered,  therefore,  that 
there  is  a  common  plane  of  rotation  for  both  the  supe- 
rior and  the  inferior  recti,  and  that  the  plane  is  ver- 
tical, forming  an  angle  of  27°  with  the  vertical  antero- 


56  THE   FUNDAMENTAL   PRINCIPLES 

posterior  plane  of  the  eye.  The  axis  of  rotation  must 
be  at 'right-angles  to  the  muscle  plane,  and  consequently 
must  form  an  angle  of  27°  with  the  transverse  axis,  but 
in  the  horizontal  plane  with  it.  The  superior  rectus 
unopposed  has  for  its  principal  effect  superversion,  and 
for  its  subordinate  results,  adversion  and  an  inward 
torsion  or  declination.  The  inferior  rectus  will  have  for 
its  principal  action  sub-version,  and  for  its  secondary  ac- 
tions, adversion  and  outward  torsion.  Thus  the  superior 
rectus,  while  being  the  chief  factor  in  a  hyperphoria, 
may  be  also  a  secondary  factor  in  the  production  of  an 
esophoria,  and  of  a  minus  cyclophoria.  The  inferior 
rectus,  while  the  chief  factor  of  a  cataphoria,  may  also 
be  a  secondary  factor  both  in  esophoria  and  in  a  plus 
cyclophoria. 

An  oblique  muscle,  when  unopposed,  is  incapable  of  a 
simple  rotation.  Its  plane  of  rotation  must  be  constructed 
in  the  same  way  as  have  been  constructed  the  planes  for 
the  recti.  In  the  case  of  the  superior  oblique,  the  point 
of  origin  through  which  the  plane  must  pass  is  the  pulley 
at  the  upper-inner  angle  of  the  orbit,  and  not  at  its  real 
origin  at  the  apex  of  the  orbit.  Since  the  inferior  oblique 
arises  beneath  this  pulley,  and  since  the  superior  oblique 
may  be  supposed  to  pass  directly  above,  while  the  inferior 
passes  directly  beneath,  the  center  of  motion  of  the  eye,  to  be 
inserted  directly  opposite  each  other  in  the  outer-posterior 


OF   OCUIvAR   ROTATIONS.  57 

quadrant,  they  may  be  said  to  have  a  common  plane  of 
rotation,  which  means,  also,  that  they  have  a  common 
axis,  around  which  each  must  revolve  the  eye  when  un- 
opposed by  any  other  muscle.  This  plane  is  at  an  angle 
of  39°  with  the  vertical  transverse  plane  of  the  eye.  The 
axis  must  be,  therefore,  at  an  angle  of  39°  with  the  visual 
axis.  When  the  superior  oblique  contracts,  its  principal 
action  is  to  tort  the  eye  in;  but  always  accompanying- this 
are  the  subordinate  actions,  sub-version  and  abversion. 
When  the  inferior  oblique  is  unopposed  and  unaided,  its 
principal  action  is  outward  torsion,  and  its  secondary  ef- 
fects are  superversion  and  abversion.  Thus  it  may  be 
seen  that  the  obliques  may  be  a  factor  in  three  forms  of 
heterophoria:  (a)  cyclophoria,  (Z>)  hyperphoria  and  cata- 
phoria,  (c)  exophoria. 

LAW  OF  MONOCULAR  MOTION. 

The  law  g'overning'  monocular  rotations  may  be  formu- 
lated as  follows:  (1)  The  visual  axis,  which  is  the  line  of 
intersection  of  the  planes  of  all  meridians,  must  be  rotated 
in  the  plane  of  that  meridian  on  which  lie  the  first  and  sec- 
ond points  of  view  and  their  retinal  images.  (2)  In  the 
plane  of  the  horizontal,  or  that  of  the  vertical,  meridian, 
the  rotation  must  be  effected  around  a  sing-le  fixed  axis, 
at  rig-ht-ang"les  to  the  rotation  plane  and  cutting-  it  at  the 
center  of  rotation — if  in  the  horizontal  plane,  around  the 


58  THE   FUNDAMENTAL   PRINCIPLES 

vertical  axis  of  the  eye;  if  in  the -vertical  plane,  around  the 
transverse  axis  of  the  eye.  (3)  In  the  plane  of  an  oblique 
rotation,  'whatever  the  degree  of  obliquity,  the  rotation 
must  be  accomplished  around  two  moving-  axes  by  two 
forces  acting  simultaneously,  these  axes  being  the  trans- 
verse and  vertical  axes,  both  at  right-angles  to  the  visual 
axis,  but  neither  one  at  rig"ht-angles  to  any  oblique  ro- 
tation plane;  while  a  third  force  prevents  any  rotation 
around  the  vistial  axis. 

The  only  part  of  the  above  law  open  to  controversy 
pertains  to  oblique  rotations.  These  rotations  are  ac- 
complished by  three  forces;  and  they  are  so  applied  as  to 
make  it  impossible  for  such  a  rotation  to  be  around  a  re- 
sultant fixed  axis,  as  would  be  the  case  if  only  two  forces 
were  acting".  If  a  resultant  axis  for  the  three  forces  be 
possible,  the  axis  would  be  a  moving"  one,  for,  in  any  ob- 
lique rotation  of  the  eye,  there  are  no  two  fixed  points, 
directly  opposite  or  otherwise  related,  on  its  surface, 
hence  there  could  be  no  fixed  diameter.  If  there  be  a 
resultant  moving  axis  for  an  oblique  rotation,  it  would 
be  hard  to  locate.  It  is  so  easy  to  grasp  the  thoug-ht 
that,  in  an  oblique  rotation,  one  oblique  muscle  prevents 
rotation  around  the  visual  axis,  while  one  rectus  muscle 
is  moving"  the  eye  around  the  vertical  axis  and  one  other 
rectus  muscle  is  moving-  the  eye  around  the  transverse 
axis,  it  seems  to  the  author  that  the  wording1  of  the  third 
section  of  the  law  of  monocular  rotation  must  be  correct. 


OF    OCULAR   ROTATIONS.  59 

The  purpose  of  the  above  law  is  that,  while  the  visual 
axis  is  being-  rotated  in  a  fixed  plane,  the  vertical  axis  of 
the  eye  shall  never  lose  parallelism  with  the  median 
plane  of  the  head,  for  on  this  parallelism  depends  correct 
orientation. 

A  single  muscle  can  obey  this  law  only  when  the  rota- 
tion is  in  the  horizontal  plane,  and  then  only  when  the 
externus  or  the  internus  is  bisected  by  this  plane.  In 
vertical  and  oblique  rotations,  an  oblique  muscle  pre- 
vents rotation  around  the  visual  axis,  hence  performs  the 
task  of  keeping1  the  vertical  axis  of  the  eye  parallel  with 
the  median  plane  of  the  head,  while  one  rectus  (as  in 
vertical  rotations),  or  at  most  two  recti  (as  in  oblique  ro- 
tations), moves  the  visual  axis  from  point  to  point  in 
space. 

In  the  light  of  this  law  the  six  extrinsic  ocular  muscles 
should  be  studied  as  they  are  related  to  each  other  in 
performing  their  tasks. 

The  helping  of  one  muscle  by  other  muscles  is  s}rner- 
gism;  the  opposing  of  one  muscle  by  other  muscles  is  an- 
tagonism. The  old  method  of  studying  these  is  set  forth 
in  the  following 

TABLE. 


I  Superior  rectus    } 

f  Synergists  . .  .  -I  [•  Tonicity. 

(  Inferior  rectus ) 


Internus 

External  rectus  . 


I  Antagonists      <  Superior  oblique '-  Tonicity. 

(  Inferior  oblique ) 


60 


THE  FUNDAMENTAL  PRINCIPLES 


{  Superior  oblique 1 

Synergists  . . .  4  >  Tonicity. 

( Inferior  oblique ) 

Externus . 

i  Internus ', 

Antagonists .  .  -<  Superior  rectus  [•  Tonicity. 

( Inferior  rectus ) 

I  Inferior  oblique Contractility 

Synergists  .  .  .  •]  A  too  high  internus,  or  }  Trmi_:tv 

e  /  A  too  high  externus  .      f  * 

Superior  rectus  in 

superversiou  ,  ,nterior  rectl]s - 

Antagonists.    |  l^?^^,,,;  or  P"-^ 

[  A  too  low  externus  .  .  .  .  j 

i.  Superior  oblique Contractility 

f  Synergists  . .  .  4  A  too  low  internus,  or  j  T>nni™+ 

,  ,     .  (  A  too  low  externus  ....?.* 

Inferior    rectus  in 

sub-version  ...  f  Supertor  retus , 

!  An^gonists.    |  ngrnus,  or 

[  A  too  high  externus  . 

(  Superior  rectus } 

f  Synergists  . .  .  •]  A  too  high  internus,  or  >  Tonicity. 

((  A  too  low  externus  .  .  .  .  ) 
[Inferior  oblique... 
Antagonists         ItoTfo^ernus,  or 
[  A  too  high  externus  . 

{Inferior  rectus  .......  } 
A  too  low  internus,  or  >•  Tonicity. 
A  too  high  externus  . .  .  ) 

Inferior  oblique  Superior  oblique 1 

Antagonists.       ^n^'Sernus,  or  ["»^- 
[  A  too  low  externus  .  .  .  .  j 

It  will  be  noticed  that  in  the  above  table  each  ocular 
muscle  has  one  more  antagonistic  muscle  than  syner- 
gistic. 


OF    OCULAR    ROTATIONS.  61 

Another  point  to  be  noted  in  the  study  of  the  table  is 
that  synergism  more  often  comes  from  tonicity  than  from 
contractility,  and  that  the  antagonism  shown  comes 
entirely  from  tonicity.  In  this  table  the  synergistic 
muscle,  either  by  tonicity  or  contractility,  aids  a  con- 
tracting" muscle  in  the  performance  of  its  principle  func- 
tion only;  and  the  antagonistic  muscle,  by  its  tonicity, 
hinders  the  contracting  muscle  in  the  performance  of  its 
principal  function  only. 

A  single  muscle  may  be  both  synergistic  and  antago- 
nistic. To  illustrate:  Rotation  directly  up  is  accom- 
plished by  two  muscles,  the  superior  rectus  and  the  in- 
ferior oblique.  The  principal  action  of  the  superior  rec- 
tus would  be  to  elevate  the  eye,  but  the  secondary  re- 
sults would  be  to  tort  the  eye  in  and  to  turn  it  in.  The 
inferior  oblique,  in  its  principal  function,  prevents  the 
intorting,  and  the  subsidiar}T  result  is  to  prevent  the  in- 
turning  and  to  help  in  the  upturning.  The  inferior  ob- 
lique is,  therefore,  both  synergistic  and  antagonistic  to 
the  superior  rectus. 

In  the  truest  sense,  a  synergistic  muscle,  by  contrac- 
tility, should  be  one  helping  another  muscle  in  the  per- 
formance of  its  task  of  rotating  the  visual  axis  correctly; 
while  an  antagonistic  muscle,  by  contractility,  should  be 
one  to  prevent  an  error  in  the  relationship  of  the  verti- 
cal axis  of  the  eye  with  the  median  plane  of  the  head. 


62  THE    FUNDAMENTAL    PRINCIPLES 

It  would  seem,  therefore,  that  a  new  table  of  syner- 
g-ism  and  antagonism  should  be  constructed,  in  which  no 
mention  of  muscles  not  contracting-  should  be  made.  Since 
this  is  a  study  of  monocular  rotation,  the  following-  table 
may  be  considered  a  study  of  the  rig-ht  eye: 

TABLE. 

(  Synergist:  None. 

(1)  Rotation  directly  to  the  right:  Externus  -j 

(  Antagonist:  None. 

(  Synergist:  None. 

(2)  Rotation  directly  to  the  left:  Internus.  .  •] 

/  Antagonist:  None. 

(  Synergist:  Inferior  oblique. 

(3)  Rotation  directly  up:  Superior  rectus  .  .  -j 

(  Antagonist:  Inferior  oblique. 

(  Synergist:  Superior  oblique. 

(4)  Rotation  directly  down:  Inferior  rectus .  < 

(  Antagonist:  Superior  oblique. 

(  Synergist:  Superior  oblique. 
f  Externus •< 

(5)  Rotation     obliquely]  (  Antagonist:  Superior  oblique, 
up-and-right -        and 

(  Synergist:  None. 
(_  Superior  rectus  .  -J 

(  Antagonist:  Superior  oblique. 

i  Synergist:  None. 
( Internus •< 

(6)  Rotation     obliquely  I  (  Antagonist:  Superior  oblique, 
down-and-left -I        and 

(  Synergist:  Superior  oblique. 
Inferior  rectus.  .  -| 

(  Antagonist:  Superior  oblique. 

(  Synergist:  None. 
Internus •< 

(7)  Rotation     obliquely]  (  Antagonist:  Inferior  oblique, 
up-and-left -j 

(  Synergist:  Inferior  oblique. 
!  Superior  rectus  .  •< 

(  Antagonist:  Inferior  oblique. 


OF    OCULAR   ROTATIONS.  63 

i  Synergist:  Inferior  oblique. 

f  Externus - 

(8)    Rotation     obliquely  j  (  Antagonist:  Inferior  oblique. 

down-and-right -j 

(  Synergist:  None, 
i  Inferior  rectus 

/  Antagonist:  Inferior  oblique. 

BINOCULAR  ROTATION. 

In  the  human  being  the  two  eyes  are  so  placed  and  so 
adjusted  as  to  make  binocular  single  vision  possible,  in 
obedience  to  the  supreme  law  of  corresponding  retinal 
points.  To  say  that  the  macula  of  one  eye  must  corre- 
spond, point  for  point,  with  the  macula  of  the  other  e}Te; 
that  the  vertical  meridian  of  one  eye  must  correspond, 
point  for  point,  with  the  vertical  meridian  of  the  other 
eye;  that  the  horizontal  meridian  of  the  one  eye,  in  like 
manner,  must  correspond  with  the  horizontal  meridian 
of  the  other  eye,  does  not  explain  the  fundamental  fact 
which  makes  binocular  single  vision  possible.  There  are 
eyes  whose  maculas  and  whose  vertical  and  horizontal 
meridians  do  not  correspond — eyes  that  have  never  had 
binocular  single  vision  and  can  never  be  made  to  have  it. 
This  abnormal  condition  was  known  to  Von  Graefe  and 
was  by  him  named  "antipathy  to  binocular  single  vi- 
sion," but  he  made  no  attempt  to  explain  it.  For  such 
eyes  there  is  no  circle  (horopter  or  monoscopter)  of  single 
seeing  with  the  two  eyes.  There  is  no  such  thing  as  a 
binocular  spacial  pole,  and  over  such  eyes  the  law  of  bin- 


64  THE   FUNDAMENTAL    PRINCIPLES 

ocular  rotation  has  no  power.  For  these  eyes,  and  they 
are  fairly  numerous,  the  fundamental  fact  underlying- 
binocular  single  vision  does  not  exist. 

"What  is  the  fundamental  fact  of  corresponding-  reti- 
nal points?"  is  a  question  worth  the  asking-.  The  au- 
thor believes  he  uttered  the  truth  when  he  taug-ht,  some 
years  ag*o,  that  the  secret  of  corresponding- retinal  points 
is  common  brain-cell  connection;  that  one  macula  corre- 
sponds, point  for  point,  with  the  other  macula  only  be- 
cause these  corresponding-  points  have,  g"oing-  from  them, 
two  fibers  which  meet  in  the  optic  tract  and  go,  side  by 
side,  back  into  the  same  cuneus  to  terminate  in  one  com- 
mon cell  in  the  visual  center.  Corresponding-  points  on 
the  two  vertical  and  the  two  horizontal  meridians,  like- 
wise corresponding  points  on  any  two  oblique  meridians 
similarly  related  to  the  vertical  and  horizontal  meridians 
and  to  the  maculas,  must  have  common  brain-cell  con- 
nection. This  explains  double  impressions,  yet  a  single 
sensation — two  images,  yet  a  single  object.  If  the  fibers 
from  the  right  macula  should  go  to  the  right  side  of  the 
brain,  and  the  fibers  of  the  left  macula  should  go  to  the 
left  side  of  the  brain,  there  would  be  two  sensations 
excited,  as  certainly  as  that  there  have  been  two  ret- 
inal impressions*  Or,  if  the  fibers  going  from  retinal 
points  that  normally  correspond,  find  their  way  back  to 
the  same  cuneus,  but  terminate  each  in  a  separate  brain- 


OF    OCUIvAR    ROTATIONS.  65 

cell,  there  would  be  two  sensations  as  certainly  as  that 
there  have  been  the  two  retinal  impressions.  One  or 
the  other  of  these  anatomic  faults  must  exist  in  every 
person  who  has  antipathy  to  binocular  vision — who  has 
never  seen  singly  with  the  two  eyes  and  who  can  never 
be  made  to  do  so.  A  good  illustration  of  common  brain- 
cell  connection  may  be  had  by  any  one  riding-  on  a  street 
car,  when  there  are  two  individuals  who  wish  to  signal 
the  conductor  their  desire  to  leave  the  car  at  the  same 
crossing.  The  two  press  the  button  at  the  same  moment 
of  time  with  but  one  result,  the  ringing  of  one  bell,  just 
as  if  only  one  button  had  been  pressed — a  double  impres- 
sion with  only  one  bell  excited.  If  one  button  were  con- 
nected with  a  bell  at  one  end  of  the  car,  while  the  other 
button  is  connected  with  a  bell  at  the  other  end  of  the  car, 
or  if  the  two  bells  be  at  the  same  end  of  the  car  and  very 
near  to  each  other,  the  pressing  of  the  two  buttons  would 
make  the  two  bells  ring,  but  their  sounds  could  not  be 
blended  into  one. 

The  law  of  visible  direction  does  not  explain  corre- 
sponding retinal  points,  for  this  law  is  violated  in  the  in- 
terest of  binocular  single  vision  whenever  the  prism  is 
placed  before  either  of  the  two  eyes.  Duction  is  possible 
only  in  violation  of  the  law  of  direction.  When  there  are 
no  corresponding  retinal  points,  nothing  can  interfere 
with  the  law  of  direction:  Everything  seen  is  on  a  line 


66  THE   FUNDAMENTAL,   PRINCIPLES 

connecting*  the  object  and  its  image,  which  line  passes 
through  the  center  of  rotation — "every  line  of  direction 
is  a  radius  of  retinal  curvature  prolonged."  Nor  is  this 
law  ever  violated  when  there  is  only  one  eye. 

A  person  whose  eyes  have  not  corresponding  retinal 
points  is  always  strabismic,  and  while  he  may  prefer  to 
use  almost  constantly  one  eye,  the  other  eye  does  not  be- 
come blind  from  want  of  use,  although  mental  suppres- 
sion alone  prevents  diplopia.  This  crossing  exists  from 
the  day  of  birth  to  the  day  of  death,  yet  the  crossed  eye 
continues  to  see  well,  whenever  permitted  to  do  so  by 
the  temporary  obstruction  of  the  other  eye.  In  ordinary 
strabismus,  as  is  well  known,  the  deviating  eye  becomes 
mentally  blind. 

Nature  has  two  methods  of  preventing  diplopia — (1) 
fusion  of  the  two  images  by  bringing  the  two  corre- 
sponding retinal  points  into  conjunction  with  the  two 
images;  (2)  mental  suppression  of  one  of  the  two  images. 
Fusion  is  possible  only  when  there  are  corresponding  reti- 
nal points.  Suppression  is  a  necessity,  (1)  when  there  are 
no  corresponding  retinal  points;  (2)  when  there  are  corre- 
sponding retinal  points,  but  mal-adjustment  of  the  ocu- 
lar muscles  makes  it  impossible  to  correctly  relate  these 
two  points  to  the  two  images  of  the  single  object. 

In  strabismic  (heterotropic)  eyes,  when  the  seeing  eye  is 
being  rotated  in  obedience  to  the  law  of  monocular  rota- 


OF    OCULAR   ROTATIONS.  67 

tion,  the  other  eye  moves,  but  not  in  the  interest  of  either 
binocular  single  vision  or  correct  orientation.  The  com- 
itant  rotation  of  a  squinting"  eye  differs  in  nothing-  from 
the  rotation  of  an  eye  that  is  stone-blind. 

Binocular  rotation,  as  it  will  now  be  studied,  is  the 
rotation  of  the  two  eyes  in  the  interest  of  binocular  sin- 
gle vision  and  correct  orientation.  Binocular  rotations 
are  either  cardinal  or  oblique.  They  are  effected  by  the 
same  muscles  that  are  concerned  in  monocular  rotations, 
but  not  wholly  by  the  volitional  brain-centers,  which 
alone  are  concerned  in  monocular  rotations.  Besides  the 
nine  conjugate  brain-centers,  all  under  the  control  of  the 
will,  and  each  connected  with  two  muscles,  one  belong- 
ing1 to  each  eye,  there  are  twelve  centers  controlled  by 
the  fusion  faculty  of  the  mind,  each  center  being  con- 
nected with  only  a  single  muscle.  These  fusion  centers, 
as  their  name  indicates,  exist  in  the  interest  of  binocular 
single  vision;  hence  when  there  is  a  condition  that  would 
cause  diplopia,  whether  the  eyes  be  at  rest  or  in  rota- 
tion, one  or  more  of  these  fusion  centers  must  be  in  ac- 
tion. These  fusion  centers  must  be  ready  to  act  both 
independently  of,  and  coordinately  with,  the  conjugate 
centers.  The  conjugate  centers  furnish  the  neuricity 
that  brings  about  all  voluntary  movements  of  the  eyes, 
such  as  verting  and  converging.  The  single  centers,  in 
the  sense  of  acting  on  only  one  muscle,  are  the  centers 


68  THE   FUNDAMENTAL,    PRINCIPLES 

that  effect  duction,  the  power  that  overcomes  double  vi- 
sion, and  planing-,  the  power  that  prevents  diplopia. 

Fig.  15  shows,  in  a  schematic  way,  the  conjugate  cen- 
ters and  the  single  fusion  centers.  This  figure  also 
shows  the  two  eyes  with  their  twelve  muscles;  but,  in 
its  study,  the  imagination  must  make  the  connections. 
In  "Ophthalmic  Neuro-Myology "  there  is  a  separate  il- 
lustration for  each  conjugate  brain-center  and  the  mus- 
cles controlled  by  it,  in  which  the  connecting  nerve-fibers 
appear;  and  the  connection  of  each  fusion  center  and  its 
muscle  is  also  shown. 

As  related  to  the  volitional  brain-centers  which  con- 
trol them,  the  twelve  muscles  belonging  to  the  two  eyes 
are  arranged  in  pairs  as  follows:  (1)  The  two  superior 
recti,  (2)  the  two  inferior  recti,  (3)  the  two  interni,  (4) 
the  right  externus  and  the  left  internus,  (5)  the  right  in- 
ternus  and  the  left  externus,  (6)  the  two  superior  ob- 
liques, (7)  the  two  inferior  obliques,  (8)  the  right  supe- 
rior oblique  and  the  left  inferior  oblique,  (9)  the  left  su- 
perior oblique  and  the  right  inferior  oblique.  For  each 
of  the  nine  groups  of  two  muscles  there  is  a  conjugate 
innervation  center  from  which  go  fibers  to  be  distributed 
equally  to  the  two  muscles  to  be  controlled  by  it.  The 
internal  recti  and  the  four  obliques  are  each  connected 
with  two  conjugate  innervation  centers,  while  the  re- 
maining muscles  are  each  under  the  control  of  only  one 
conjugate  innervation  center. 


OF  OCULAR  ROTATIONS.  69 

THE  INNERVATIONS. 

To  accomplish  their  work  these  muscles  have  nine 
conjugate  innervations: 

(1)  The  one  to  elevate  both  eyes. 

(2)  The  one  to  depress  both  eyes. 

(3)  The  one  to  converge  both  eyes. 

(4)  The  one  to  move  both  eyes  to  the  right. 

(5)  The  one  to  move  both  eyes  to  the  left. 

(6)  The  one  to  keep  the  vertical  axes  from  diverging 
above. 

(7)  The  one  to  prevent  their  converging  above.   These 
(6  and  7)  are  called  into  action  by  the  guiding  sensation, 
when  the  point  of  view  is  primary  or  in  either  one  of  the 
four  cardinal  directions. 

(8)  The  one  to  maintain  the  parallelism  of  the  vertical 
axes  and  the  median  plane  of  the  head  when  the  point  of 
view  is  obliquely  up  and  to  the  right,  or  down  and  to  the 
left;  and 

(9)  The  one  to  maintain  the  parallelism  of  the  vertical 
axes  of  the  eyes  and  the  median  plane  of  the  head,  when 
the  point  of  view  is  obliquely  up  and  to  the  left,  or  down 
and  to  the  right. 

The  innervations  one  to  five  are  for  the  recti,  and 
the  sixth,  seventh,  eighth,  and  ninth  are  for  the  ob- 
liques. Each  of  the  conjugate  innervation  centers  con- 


70  THE    FUNDAMENTAL   PRINCIPLES 

trols  one  of  the  several  pairs  of  muscles.  The  first  con- 
trols the  two  superior  recti;  the  second,  the  two  inferior 
recti;  the  third,  the  two  interni;  the  fourth,  the  right  ex- 
ternus  and  the  left  internus;  the  fifth,  the  right  internus 
and  the  left  extern  us;  the  sixth,  the  two  superior  ob- 
liques; the  seventh,  the  two  inferior  obliques;  the  eighth, 
the  right  superior  oblique  and  the  left  inferior  oblique; 
the  ninth,  the  left  superior  oblique  and  the  right  inferior 
oblique.  The  verting  centers  act  singly  only  in  the 
sweeping  of  the  eyes  in  the  horizontal  plane;  they  act  in 
pairs  only  when  the  eyes  are  moved  directly  up  or  down; 
three  of  these  centers  act  together  in  oblique  rotations 
of  the  eyes.  It  is  only  in  oblique  rotations  that  nor- 
mal ocular  muscles  need  any  other  centers  of  nerve- 
power  than  the  conjugate  centers  already  studied. 
Eyes  whose  muscles  are  unequal  in  tonicity  cannot  have 
binocular  single  vision  when  controlled  only  by  the  con- 
jugate innervation  centers,  or  even  when  at  rest.  Ob- 
lique rotations  of  eyes  with  normal  muscles,  and  rota- 
tions of  any  character,  or  even  rest,  when  muscles  are 
unequal  in  tone,  require  that  there  shall  be  emergency 
or  fusion  brain-centers,  one  for  each  individual  muscle. 
These  centers,  twelve  in  number,  are  certainly  not  under 
control  of  the  will.  They  exist  in  the  interest  of  binoc- 
ular single  vision,  and,  therefore,  may  be  said  to  be 
tinder  the  control  of  the  fusion  faculty  of  the  mind. 


OF   OCULAR   ROTATIONS.  71 

Their  location  is,  probably,  at  the  base  of  the  brain;  and 
certainly  each  of  these  centers  has  power  over  one  ocu- 
lar muscle.  Six  of  these  fusion  centers  must  be  on 
either  side  of  the  brain.  These  should  be  numbered  in 
harmony  with  the  numbering-  of  the  conjugate  centers, 
and  the  same  number  should  be  given  to  two  basal  cen- 
ters, the  words  right  and  left  to  distinguish  the  one  from 
the  other.  The  right  first  center  belongs  to  the  right 
superior  rectus,  and  the  left  first  center  belongs  to  the 
left  superior  rectus;  the  right  second  center  belongs  to 
the  right  inferior  rectus,  and  the  left  second  center  be- 
longs to  the  left  inferior  rectus;  the  right  third  center 
belongs  to  the  right  internus,  and  the  left  third  center 
belongs  to  the  left  internus;  the  right  fourth  center  be- 
longs to  the  right  externus,  and  the  left  fourth  center 
belongs  to  the  left  externus;  the  right  sixth  center  be- 
longs to  the  right  superior  oblique,  and  the  left  sixth 
center  belongs  to  the  left  superior  oblique;  the  right 
seventh  center  belongs  to  the  right  inferior  oblique,  and 
the  left  seventh  center  belongs  to  left  inferior  oblique. 
When  one  of  these  basal  centers  discharges  neuricity, 
only  a  single  muscle  responds;  when  a  conjugate  center 
discharges  neuricity,  both  muscles  of  a  pair  respond. 

The  necessity  for  the  existence  of  both  the  conjugate 
volitional  centers  and  the  basal  fusion  centers  is  shown 
in  Fig.  14,  which  will  now  be  studied.  A  careful  study 


72 


THE  FUNDAMENTAL  PRINCIPLES 


**• 

H- 

bi) 


OF    OCULAR   ROTATIONS.  73 

of  this  figure  will  bring-  many  things  into  the  light  of  the 
understanding.  First  of  all,  the  figure  shows  three 
planes  —  (1)  the  fixed  horizontal  plane  of  the  head, 
a-b-c-d;  (2)  the  fixed  vertical  plane  of  the  head,  g-h-i-j ; 
(3)  Listing's  plane,  or  the  fixed  transverse  plane  of  the 
head,  cutting  the  centers  of  the  two  eyes,  this  plane  be- 
ing k-l-m-n.  Each  of  these  planes  is  at  right-angles  to 
the  other  two  planes,  and  the  three  lines  of  intersec- 
tion are  e-f,  a-b,  and  h-g.  In  the  horizontal  plane  are 
shown  horizontal  sections  of  the  two  eyes,  r  and  s,  and 
the  two  visual  axes  are  ry  and  s-f. 

PLANES  OF  REFERENCE. 

The  extended  fixed  vertical  and  horizontal  planes  of 
the  head  are  planes  of  reference.  With  the  head  in  the 
primary  position,  if  a  point  is  not  in  the  horizontal  plane, 
a-b-c-d,  it  is  instantly  known  to  be  above  or  below  it;  if 
a  point  is  not  in  the  vertical  plane,  h-i-j-k,  it  is  certainly 
known  to  be  to  the  right  or  left  of  it;  and  an  approxi- 
mately correct  estimate  of  the  degrees  of  removal  of 
such  point  from  these  planes  can  be  made  in  obedience 
to  the  law  of  visible  direction.  In  the  primary  position 
of  the  head,  the  plane  a-b-c-d  is  horizontal,  and  the  eyes 
are  in  their  primary  positions  when  the  two  visual  axes 
lie  in  this  plane,  and  are  converged  on  some  point,  at 
practical  infinity,  lying  on  the  line  of  intersection,  e-f,  of 


74  THE   FUNDAMENTAL   PRINCIPLES 

the  horizontal  and  vertical  planes.  Converged  on  such 
a  point,  the  visual  axes  are  practically,  though  never 
really,  parallel.  To  be  perfectly  parallel,  the  visual 
axis  (r-f)  of  the  right  eye  would  have  to  be  in  the  posi- 
tion r-f",  and  the  visual  axis  (s-f)  of  the  left  eye  would 
have  to  be  s-f. 

In  locating  the  position  of  any  point  in  viewable  space, 
the  word  right  and  left  would  be  used  in  reference  to  the 
vertical  plane  of  the  head,  h-i-j-k;  the  words  above  and 
below  would  be  used  in  reference  to  the  horizontal  plane, 
a-b-c-d;  and  the  word  in  should  be  used  in  reference  to 
both  the  vertical  and  horizontal  planes.  The  points/"' 
and/"  are  in  the  horizontal  plane,  the  one  to  the  right, 
the  other  to  the  left,  of  the  vertical  plane;  the  points  z 
and  z  are  in  the  vertical  plane,  respectively  above  and 
below  the  horizontal  plane.  All  points  lying  on  the  line 
of  intersection  (e-f]  of  the  two  planes  would  be  points 
directly  ahead,  and  these  would  be  primary  points  of 
view.  All  points  off  this  line  of  intersection  (e-f)  would 
be  secondary  points  of  view.  The  four  cardinal  direc- 
tions a.rzf-i,f-j,f-c,  zndf-d.  All  points  not  in  the  line 
c-d  (or  in  the  plane  a-b-c-d)  and  not  in  the  line  i-j  (or  in 
the  plane  g-h-i-j)  are  obliquely  related  to  these  lines  (or 
planes).  The  point  of  binocular  view — whether  direct, 
cardinal,  or  oblique — is  the  point  of  intersection  of  the 


OF    OCULAR    ROTATIONS.  ?D 

visual  axes,  to  be  studied  a  little  further  on  as  the  binoc- 
ular spacial  pole. 

With  the  head  fixed  in  the  primary  position,  the  point 
of  binocular  view  may  be  changed  from  the  primary 
point,/",  to  any  secondary  point,  whether  cardinal  or  ob- 
lique, in  obedience  to  the  law  of  binocular  rotation.  The 
absurdity  of  the  claim  that  the  axes  of  all  binocular  ro- 
tations, from  the  primary  to  a  secondary  point  of  view, 
or  vice  versa,  must  lie  in  Listing's  plane,  is  made  appar- 
ent by  even  a  casual  study  of  Fig.  14.  In  this  figure, 
k-l-m-n  represents  Listing's  plane,  which  is  at  right-an- 
gles to  the  planes  a-b-c-d  and  h-i-j-k.  Listing's  plane 
is,  therefore,  a  transverse  vertical  plane  of  the  head,  and 
it  cuts  the  centers  of  rotation  of  the  two  eyes.  It  has 
been  shown  that  the  axes  of  all  rotations  lie  in  the  plane 
of  the  equator  of  the  eye,  and  that  the  equatorial  plane 
is  always  at  right-angles  to  the  visual  axis.  Therefore, 
with  every  change  in  the  position  of  the  visual  axis, 
there  must  be  a  change  in  the  relationship  of  the  plane 
of  the  equator  with  Listing's  plane.  There  is  only  one 
point  in  the  plane  of  the  equator  that  never  leaves  the 
Listing  plane,  and  that  is  the  center  of  rotation.  Since 
the  transverse  and  vertical  axes  of  the  eyes,  alone  or  to- 
gether, are  the  only  axes  of  rotations,  the  relationship 
that  these  bear  to  Listing's  plane  is  determined  by  the 
relationship  that  the  visual  axes  bear  to  the  fixed  verti- 


76  THE   FUNDAMENTAL   PRINCIPLES 

cal  and  horizontal  planes  of  the  head.  When  the  visual 
axes,  r-f  and  s-f,  lie  in  the  plane  a-b-c-d,  the  vertical 
axes  of  the  eyes  must  be  in  Listing's  plane.  Any  move- 
ment of  the  eye  that  compels  the  visual  axis  to  remain  in 
the  plane  a-b-c-d,  as  from/"  to/'  or  from  fiof",  must  be 
around  the  vertical  axis,  which  must  lie  in  Listing's 
plane.  Any  rotation  around  the  transverse  axis  will 
carry  the  point  of  fixation  up  to  z  or  down  to  z',  but  in 
these  rotations  the  transverse  axis  of  each  eye  forms  the 
same  angle  with  a-b  that  r-f  and  s-f  form  with  e-f,  hence 
the  rotation  from  f  to  z  or  z  is  about  an  axis  that  does 
not  lie  in  Listing's  plane,  any  more  nearly  than  is 
there  parallelism  of  r-/"and  s-f  with  e-f.  If  the  rota- 
tion upward  were  to  start  from/",  the  axis  of  rotation 
of  the  left  eye  would  lie  in  Listing's  plane,  for  the 
visual  axis,  in  position  of  s-f ,  would  be  parallel  with  e-f; 
but  the  axis  of  the  right  eye  would  form  the  same  angle 
with  Listing's  plane  as  its  visual  axis,  in  the  position  of 
r-f ,  forms  with  e-f.  In  a  rotation  starting  upward  from 
a  point  between  /and/'  or  beyond/',  neither  of  the  two 
axes  of  rotation  would  lie  in  Listing's  plane. 

The  conclusion  compelled  by  the  above  study  of  Fig. 
14  is  that  Listing's  plane  cannot  be  a  plane  of  reference, 
nor  can  it  be  a  plane  containing  the  axes  of  all  rotations 
starting  from,  or  returning  to,  the  primary  point  of  view. 
The  equatorial  plane  of  the  eye  contains  both  the  verti- 


OF    OCULAR    ROTATIONS.  77 

cal  and  transverse  axes  of  the  eye,  and  it  is  around  one 
or  the  other  or  both  of  these  that  all  rotations,  car- 
dinal and  oblique,  occur.  Listing's  plane,  like  List- 
ing's law,  should  be  forgotten  in  the  interest  of  truth. 

BRAIN-CENTERS  FOR  BINOCULAR  ROTATIONS. 

These  brain-centers,  volitional  and  fusional,  have  al- 
ready been  named.  The  study  of  Fig.  14  will  convince 
even  a  skeptic  that  these  centers  are  real  and  not  imag- 
inary. The  convergence  of  the  visual  axes,  r-/"and  s-f, 
to  any  point  on  e-f,  is  effected  by  the  3rd  volitional 
center  acting  on  both  interni;  turning  the  visual  axes 
from  f  to/"  is  accomplished  by  the  4th  volitional  cen- 
ter acting  on  the  right  externus  and  the  left  internus; 
sweeping  the  visual  axes  from  ftof  is  made  possible  by 
the  action  of  the  5th  volitional  center  on  the  right  in- 
ternus and  the  left  externus.  The  above  centers  have 
been  pointed  out  first  because  they  effect  the  simpler  ro- 
tations. 

More  complicated  are  the  rotations  directly  up  and 
down.  Elevating  the  visual  axes  from^to  z  is  accom- 
plished by  the  combined  activity  of  two  volitional  cen- 
ters— (a)  the  1st  conjugate  acting  on  the  two  superior 
recti,  and  (b)  the  7th  conjugate  acting  on  the  two  in- 
ferior obliques.  Depressing  the  visual  axes  from  f  to 
z  is  effected  by  the  harmonious  activity  of  two  volitional 


78  THE    FUNDAMENTAL    PRINCIPLES 

centers — (a)  the  2nd  conjugate  acting  on  the  inferior 
rectus  of  each  eye,  and  (b)  the  6th  conjugate  acting  on 
the  two  superior  obliques. 

More  complicated  still  are  oblique  rotations,  for  each 
of  these  must  be  effected  by  the  harmonious  action  of 
three  volitional  brain-centers;  and,  in  addition  to  these, 
every  oblique  rotation  requires  activity  on  the  part  of 
two  basal  or  fusion  centers.  If  the  visual  axes  are  to  be 
moved  from  fto  any  point  above  the  horizontal  plane  and 
to  the  right  of  the  vertical  plane,  this  motion  must  re- 
sult from  the  harmonious  action  of  the  1st  conjugate 
center  on  the  two  superior  recti,  the  4th  conjugate  on 
the  right  externus  and  left  internus,  and  the  8th  con- 
jugate on  the  right  superior  oblique  and  the  left  inferior 
oblique.  In  the  right-sweep  part  of  this  rotation,  since 
the  left  inferior  oblique  would  hinder  the  left  internus, 
while  the  right  superior  oblique  would  help  the  right  ex- 
ternus, the  hindered  left  internus  must  receive  a  supple- 
mental impulse  from  the  left  3rd  basal  or  fusion  center, 
whose  sole  power  pertains  to  that  muscle.  Since,  in  the 
upward  part  of  this  oblique  rotation,  the  right  superior 
rectus  would  be  hindered  by  the  right  superior  oblique, 
while  the  left  superior  rectus  would  be  helped  by  the  left 
inferior  oblique,  the  hindered  right  superior  rectus  must 
receive  supplemental  neuricity  from  the  right  1st  basal 
center,  else  the  right  visual  axis  would  lag  behind  the 


OF    OCULAR    ROTATIONS.  79 

left  visual  axis.  Whatever  the  degree  of  obliquity  and 
in  whatsoever  direction,  the  rotation  must  be  accom- 
plished by  the  harmonious  action  of  three  conjugate  vo- 
litional centers  and  two  basal  or  fusion  centers. 

In  order  to  bring"  into  view  the  only  remaining1  conju- 
gate brain-center  connected  with  the  extrinsic  ocular 
muscles  while  studying-  Fig-.  14,  the  rotation  may  be  con- 
sidered as  from/" to  a  point  above  the  horizontal  plane 
and  to  the  left  of  the  vertical  plane.  This  point  can  be 
reached  only  as  the  result  of  the  harmonious  activity 
of  the  1st,  5th,  and  9th  conjugate  centers.  The  left 
superior  rectus,  hindered  by  the  left  superior  oblique, 
must  receive  supplemental  neuricity  from  the  left  1st 
basal  center;  and  the  right  internus,  hindered  by  the  right 
inferior  oblique,  must  receive  supplemental  neuricit}rfrom 
the  right  3rd  basal  center.  In  like  manner  might  be 
studied  rotations  from/"  to  some  point  below  the  horizon- 
tal plane  and  to  the  left  of  the  vertical  plane,  or  to  some 
point  below  the  horizontal  plane  and  to  the  right  of  the 
vertical  plane,  but  in  every  such  study  the  fact  would  be- 
come apparent  that  three  volitional  and  two  fusion  cen- 
ters have  been  acting  in  the  interest  of  binocular  single 
vision  and  correct  orientation. 

In  every  rotation  above  the  horizontal  plane,  a-b-c-d, 
the  1st  conjugate  center  participates;  in  every  rotation 
below  this  plane  the  2nd  conjugate  center  has  a  part. 


80  THE    FUNDAMENTAL   PRINCIPLES 

In  every  rotation  to  the  right  of  the  vertical  plane,  g-h-i-j, 
the  4th  conjugate  center  is  active,  and  in  every  rota- 
tion to  the  left  of  this  plane  the  5th  conjugate  center 
participates.  The  3rd  conjugate  center  is  concerned 
in  the  fixing  of  any  point  in  space.  Thus  the  five  con- 
jugate centers  controlling  the  four  recti  muscles,  become 
more  real  when  studied  in  the  light  of  Fig.  14. 

Rotation  from/"  to  any  point  in  space  above  or  below 
the  horizontal  plane,  a-b-c-d,  must  call  into  action  some 
one  of  the  four  conjugate  centers  connected  with  the  ob- 
lique muscles.  In  rotations  from /"to  z,  the  7th  conju- 
gate center  keeps  the  vertical  axes  of  the  eyes  parallel 
with  the  vertical  plane,  g-h-i-j',  and  in  rotations  from/" to 
z ',  the  6th  conjugate  center  maintains  this  parallelism. 
In  rotations  up-and-to-the-right  and  down-and-to-the- 
left,  the  8th  conjugate  center  prevents  torsioning  to- 
ward the  right;  and  torsioning  toward  the  left  is  pre- 
vented by  the  9th  conjugate  center  when  the  rotations 
are  up-and-to-the-left  and  down-and-to-the-right.  Ac- 
tivity of  the  8th  and  9th  conjugate  centers  arouses  into 
action  six  of  the  right  and  left  fusion  or  basal  centers 
belonging  to  the  recti,  but  only  two  of  these  at  any  one 
time.  The  two  basal  centers  never  excited  in  oblique 
rotations  of  eyes  whose  muscles  are  normal,  are  the 
right  4th  and  the  left  4th.  Cardinal  rotations  by  nor- 
mal muscles  do  not  excite  a  single  fusion  center.  Thus 


OF    OCULAR   ROTATIONS.  81 

far  the  study  of  Fig1.  14  has  demonstrated  the  existence 
of  all  of  the  nine  conjugate  brain-centers  belonging"  to 
the  recti  and  obliques,  and  six  of  the  eight  right  and 
left  basal  or  fusion  centers  connected  with  the  recti. 

The  demonstration  of  the  fact  of  the  existence  of  the 
right  and  left  individual  fusion  centers  connected  with 
the  recti,  and  the  four  like  centers  connected  with  the 
obliques,  is  made  easy  by  a  further  study  of  Fig.  14.  Nor- 
mal recti  muscles,  in  a  state  of  tonicity,  would  converge 
the  visual  axes  at/",  if  that  point  were  twenty  feet  distant, 
and  would  keep  the  two  visual  axes  in  the  plane  a-b-c-d\ 
and  the  obliques  of  equal  tonicity  would  confine  the  two 
horizontal  retinal  meridians  in  this  plane.  In  such  a 
condition  of  equal  tonicity,  neither  volitional  nor  fusion 
brain-centers  are  active,  when  both  the  head  and  the  eyes 
are  in  their  primary  positions.  Convergence  of  the  visual 
axes  and  planing  these  axes  and  the  horizontal  meridians 
are  conditions  essential  to  binocular  single  vision;  but  the 
existence  of  single  vision  with  the  two  eyes  does  not 
guarantee  that  all  the  muscles  are  normal  in  tone.  If 
tonicity  cannot  effect  binocular  single  vision,  this  must  be 
accomplished  by  contractility  of  the  muscles  wanting  in 
tone.  The  source  of  the  required  neuricity  is  not  con- 
trolled by  the  will,  but  by  the  fusion  faculty  of  the  mind, 
itself  dominated  by  the  desire  for  single  vision.  Every 
ocular  muscle  has  its  individual  fusion  center,  the  neu- 


82  THE   FUNDAMENTAL   PRINCIPLES 

ricity  from  which  acts  on  only  the  one  muscle.  These 
centers  have  already  been  individualized  by  numbers, 
and  the  existence  of  six  of  the  right  and  left  fusion  cen- 
ters for  the  recti  has  been  proved  in  the  study  of  oblique 
rotations,  in  the  light  of  Fig.  14.  By  means  of  this  fig- 
ure the  existence  of  all  the  fusion  centers,  eight  for  the 
recti  and  four  for  the  obliques,  can  be  demonstrated 
from  two  different  vantage  grounds — viz.,  the  tests  for 
heterophoria  and  the  duction  tests. 

The  proof,  from  the  standpoint  of  heterophoric  tests, 
will  presuppose  the  uncomplicated  existence  of  each  of 
the  several  errors  to  be  studied  in  Chapter  III.  One 
eye  must  be  taken  off  its  guard  in  order  that  any  one  of 
these  errors  may  become  manifest.  The  placing  of  a  6° 
prism,  base  up,  before  the  right  eye  in  Fig.  14,  would 
double/",  the  false  f  being  thrown  to  the  position  of  /. 
The  right  eye  now  off  its  guard  will  assume  the  position 
that  muscle  tonicity  would  give  to  it,  and  not  a  single 
muscle  belonging  to  this  eye  will  receive  neuricity  from 
any  source,  provided  the  mind  uses  the  left  eye  for  fixing 
the  true/.  If  the  false  /"be  directly  under  the  true/",  it 
thus  appears  because  the  externus  and  internus  of  the 
right  eye  have  equal  tonicity,  and  the  visual  axis  of  this 
eye,  notwithstanding  the  prism  diplopia,  will  be  pointing 
to  the  true/.  By  removal  of  the  prism  the  diplopia  is 
made  to  disappear  without  the  turning  of  either  eye. 


OF    OCULAR    ROTATIONS.  83 

If  the  false/",  instead  of  being-  at  z\  stands  directly  under 
f",  it  is  so  because  the  right  eye,  in  assuming'  its  position 
of  rest,  has  its  visual  axis  pointing  to  f  (esophoria).  On 
removing"  the  prism  the  false  /  would  jump  into  the 
position  of  f"  and  would  remain  there  so  long1  as  the 
right  visual  axis  points  to/'.  This  diplopia  would  not 
be  tolerated.  To  overcome  it,  the  fusion  faculty  would 
unlock  the  right  4th  basal  center  and  cause  neuricity 
to  flow  to  the  rig-ht  externus,  whose  contraction  would 
pull  the  eye  so  as  to  quickly  bring-  its  visual  axis  from/' 
to/".  The  left  eye,  throughout  the  diplopia,  and  during 
the  recovery  of  binocular  single  vision,  has  remained  sta- 
tionary, for  it  has  received  no  fusion  impulse.  The  right 
fourth  basal  center  alone  has  acted,  and  only  the  exter- 
nal rectus  of  the  right  eye  has  responded.  Any  impulse 
to  any  muscle  of  the  left  eye  would  have  made  the  vis- 
ual axis  leave  the  point/".  In  the  same  manner  the  left 
eye  could  be  tested,  and  by  the  test  the  left  4th  fu- 
sion center  could  be  found. 

Placing  the  prism,  base  up,  before  the  right  eye,  the 
false  f  would  be  thrown  directly  down  to  z'\  but  instead 
of  appearing  directly  below/",  it  would  seem  to  be  under 
f ,  and  only  because  excessive  tonicity  of  the  externus  of 
the  right  eye  (exophoria)  has  turned  it  out  so  that  its  vis- 
ual axis  points  tof".  On  removing  the  prism  the  false/ 
would  jump  to  the  position  off  and  would  remain  there 


84  THE    FUNDAMENTAL    PRINCIPLES 

if  no  fusion  effort  were  made;  but  instantly  the  right 
3rd  fusion  center  alone  would  be  excited,  and  its  dis- 
charged neuricity  would  compel  the  right  internus  to 
pull  the  right  eye  so  that  its  visual  axis  shall  move  from 
f"  to  f.  In  this  fusion  effort  not  a  muscle  connected 
with  the  left  eye  has  received  any  impulse,  else  its  vis- 
ual axis  would  have  been  carried  away  from  point  f. 
By  applying  the  test  to  the  left  eye,  the  existence  of  the 
left  3rd  basal  center  could  be  demonstrated. 

By  placing  a  10°  prism,  base  in,  before  the  right  eye,  a 
false /"would  be  thrown  to  d.  If  the  false/  appears  to 
be  at  d,  it  is  because  of  the  fact  that  the  superior  and 
inferior  recti  of  the  right  eye  are  equal  in  tonicity;  and 
notwithstanding  the  diplopia,  the  right  visual  axis  con- 
tinues to  point  to/.  Removal  of  the  prisrn  makes  the 
false/ jump  at  once  into  the  true/,  and  that,  too,  with- 
out any  movement  of  either  eye.  But  if  the  false  f 
appears  under  d,  on  a  level  with  z ,  it  is  because  the  right 
superior  rectus,  endowed  with  an  excess  of  tonicity 
(hyperphoria),has  elevated  the  eye  so  that  its  visual  axis 
points  to  z.  On  removal  of  the  prism  the  false  f  would 
jump  into  z'  and  would  remain  there  if  no  effort  at  fusion 
were  put  forth;  but  this  effort  at  fusion  will  be  made 
and  the  diplopia  will  disappear.  The  power  this  time 
comes  from  the  right  2nd  basal  center,  and  it  acts  only 


OF    OCULAR    ROTATIONS.  85 

on  the  right  inferior  rectus,  which  at  once  turns  the  eye 
down  so  that  its  visual  axis  shall  point  to  /. 

With  the  10°  prism,  base  in,  before  the  right  eye,  the 
false  f  may  be  made  to  appear  above  d,  on  a  level 
with  z,  because  of  excessive  tonicity  on  the  part  of  the 
right  inferior  rectus  (cataphoria).  Now  the  right  visual 
axis  will  point  to  z .  On  removal  of  the  prism  the  false 
/  will  jump  into  z  and  will  remain  there,  should  the  right 
visual  axis  continue  to  point  to  z  .  To  overcome  this 
diplopia,  the  right  1st  basal  center  calls  into  action  the 
right  superior  rectus  alone,  and  by  this  action  the  right 
eye  is  elevated  so  that  its  visual  axis  may  point  to/",  the 
diplopia  disappearing  at  that  moment. 

The  existence  of  the  rig-Jit  1st  and  2nd  basal  or  fu- 
sion centers  has  thus  been  proved  from  a  second  stand- 
point. Placing  the  10°  prism  before  the  left  eye,  the 
fact  of  the  existence  of  the  left  1st  and  2nd  fusion 
centers  can  be  shown.  The  eight  fusion  centers,  each 
controlling  a  single  rectus  muscle  in  the  interest  of 
binocular  single  vision,  certainly  exist. 

A  Maddox  triple  rod  placed  vertically  before  each  eye, 
with  a  6°  prism,  base  up,  behind  the  right  rod,  will  make 
two  streaks  of  light  when  a  candle  or  gas  jet  is  the  test 
object.  The  upper  streak  should  be  fixed.  If  the  lower 
streak  is  parallel  with  the  upper  one,  it  is  because  the 
right  superior  and  inferior  obliques  are  equal  in  tonicity. 


86  THE   FUNDAMENTAL    PRINCIPLES 

If  the  lower  streak  diverges  from  the  upper  at  their  left 
ends,  it  is  because  the  right  inferior  oblique,  possessing 
an  excess  of  tonicity,  has  tilted  the  horizontal  retinal 
meridian  down  at  the  right  (plus  cyclophoria).  Remov- 
ing the  6°  prism,  the  two  streaks  can  be  made  to  blend 
throughout  only  because  the  right  6th  fusional  or  bas- 
al center  compels  the  right  superior  oblique  to  restore 
the  horizontal  retinal  meridian  to  its  correct  position  in 
the  horizontal  plane,  a-b-c-d.  No  other  center  has  acted 
on  any  other  muscle  connected  with  either  eye.  If,  with 
the  prism  behind  the  right  rod,  the  lower  streak  has 
lost  parallelism  by  leaning  down  to  the  right,  this  would 
be  due  to  the  fact  that  the  right  superior  oblique,  with 
excessive  tonicity,  has  torted  the  right  eye  in  (minus 
cyclophoria).  On  removal  of  the  prism  the  two  streaks 
could  blend  only  because  of  activity  of  the  7th  basal 
center  compelling  the  weak  inferior  oblique  to  replace 
the  horizontal  meridian  in  the  horizontal  plane,  from 
which  it  had  been  thrown  when  the  eye  was  off  its  guard. 
Thus  has  it  been  proved  that  there  are  right  6th  and 
7th  basal  or  fusion  centers.  By  placing  the  prism 
behind  the  left  rod,  the  fact  of  the  existence  of  the 
left  6th  and  7th  basal  or  fusion  centers  is  also  prov- 
able. 

No  additional  proof  should  be  necessary  in  order  to 
convince  even  the  most  skeptical  concerning  the  twelve 


OF    OCULAR    ROTATIONS.  87 

fusion  centers,  and  the  tasks  they  are  set  to  perform. 
The  one  remaining'  method  of  proving-  their  existence 
is  the  duction  test.  This  must  be  studied  in  connection 
with  Fig.  14,  in  order  that  the  whole  truth  may  be  told 
about  them. 

The  best  means  for  taking-  the  duction  power  of  the 
recti  muscles  is  the  rota.ry  prism  of  the  Monocular  Pho- 
rometer,  but  this  test  may  be  made  by  means  of  the  loose 
prism  in  the  refraction  case.  With  the  rotary  prism,  the 
fusion  centers  involved  will  discharg-e  neuricity  in  in- 
creasing1 quantity,  as  the  imag-e  is  being-  gradually  moved, 
up  to  the  point  when  fusion  is  no  longer  possible.  The 
placing-  of  a  loose  prism  before  the  eye  excites  suddenly 
and  to  the  full  extent  the  fusion  center  and  the  muscle 
under  its  control.  In  the  former  method  the  eye  glides 
g-ently;  in  the  latter  method  the  eye  jumps  violently. 
Each  method  is  as  capable  as  the  other  in  proving-  the 
existence  of  the  individual  fusion  centers  connected  with 
the  recti  muscles.  Since  the  author  prefers  the  revolv- 
ing- prism,  that  method  will  be  made  to  give  evidence 
concerning  the  existence  of  these  centers  in  the  still  fur- 
ther study  of  Pig.  14.  The  phorometer,  without  the 
supernumerary  displacing  prism,  should  be  placed  in 
front  of  the  right 'eye  in  position  for  taking  abduction 
and  adduction.  With  the  index  at  zero,  the  two  or- 
thophoric  eyes  will  fix  the  pointy  as  a  result  of  muscle 


88  THE    FUNDAMENTAL    PRINCIPLES 

tonicity  only.  By  turning-  the  index  in  the  temporal  arc, 
the  image  of  /on  the  right  retina  will  be  carried  nasal- 
ward — that  is,  toward  e — in  that  eye.  The  only  way  to 
prevent  diplopia  is  for  the  macula  to  keep  under  the  mov- 
ing image.  Since  the  image  is  moving  nasal-ward  on 
the  horizontal  meridian,  the  macula  must  move  directly 
nasal-ward  and  in  no  other  direction.  This  motion  of  the 
eye  is  accomplished  by  a  discharge  of  neuricity  from  the 
right  4th  basal  center  to  the  right  externus  alone. 
During  this  revolution  of  the  prism,  no  other  brain-cen- 
ter has  been  excited,  and  no  other  ocular  muscle  has 
contracted. 

When  the  index  has  been  returned  to  zero,  there  is 
easy  binocular  vision  at  the  expense  of  muscle  tonicity 
only.  Revolving  the  index  of  the  prism  into  the  nasal 
arc  will  make  the  image  of  f  move  temple-ward — that  is, 
toward  a.  At  the  very  beginning  of  the  rotation  of  the 
prism  the  right  3rd  fusion  center  becomes  active,  and 
the  neuricity  from  it  makes  the  right  internus  move  the 
eye  so  that  the  macula  may  remain  beneath  the  moving 
image.  This  action  of  the  right  3rd  fusion  center  on 
the  right  internus  alone,  has  prevented  diplopia.  No  im- 
pulse has  gone  from  any  other  center  to  any  other  muscle 
belonging  to  either  eye.  Thus  abduction  and  adduction 
of  the  right  eye  prove  the  existence  of  the  rig-Jit  4th 
and  3rd  fusion  centers.  In  the  same  manner  abduction 


OF   OCULAR    ROTATIONS.  89 

and  adduction  of  the  left  eye  may  be  made  to  prove  the 
existence  of  the  left  4th  and  3rd  fusion  centers. 

The  prism  should  now  be  placed  before  the  right  eye 
for  the  taking"  of  superduction  and  subduction.  With 
the  index  at  zero,  the  two  orthophoric  eyes  will  have  easy 
binocular  single  vision  at  the  expense  of  muscle  tonicity 
only.  When  the  index  is  being  rotated  into  the  upper 
arc,  the  image  of  f  on  the  right  retina  is  made  to  move 
downward  on  the  vertical  meridian.  The  macula  must 
remain  under  the  moving  image,  else  the  object/  will  be 
doubled,  the  false  /"appearing  directly  above  the  true  f. 
This  moving  of  the  macula  is  made  possible  by  the  con- 
traction of  the  right  superior  rectus,  in  response  to  an 
impulse  coming  from  the  right  1st  fusion  center.  No 
other  muscle  contracts,  nor  does  any  other  center  dis- 
charge neuricity  for  effecting  this  fusion.  Returning 
the  index  to  zero  relieves  both  the  right  1st  fusion  cen- 
ter and  the  right  superior  rectus  from  further  activity. 
If  the  index  is  now  made  to  move  downward,  the  image 
of  f  on  the  right  retina  will  be  moved  upward  on  the  ver- 
tical meridian.  The  macula  must  be  kept  under  the 
moving  image  or  a  false  /"will  appear  directly  below  the 
true  f.  To  prevent  this  diplopia,  the  right  2nd  fusion 
center  will  be  made  to  discharge  neuricity  to  the  right 
inferior  rectus  alone.  No  other  center  and  no  other  mus- 
cle will  be  brought  into  action  for  maintaining  this  fu- 


90  THE   FUNDAMENTAL   PRINCIPLES 

sion,  and  this  center  and  its  muscle  cease  activity  the 
moment  the  index  is  returned  to  zero.  Thus  the  taking- 
of  right  superduction  and  subduction  proves  the  exist- 
ence of  the  right  1st  and  2nd  fusion  centers.  By  plac- 
ing1 the  prism  before  the  left  eye  in  position  for  tak- 
ing- left  superduction  and  subduction,  the  existence  of 
the  left  1st  and  2nd  fusion  centers  may  be  proved. 

In  all  these  duction  tests  it  will  be  observed  that  fusion 
has  been  accomplished  in  violation  of  the  law  of  direction 
as  it  applies  to  the  rig-lit  eye.  As  the  macula  moves  in, 
the  visual  axis  moves  from  y7  toward  /"';  as  the  macula 
moves  out,  the  visual  axis  moves  f rom  f  toward/"';  as 
the  macula  moves  downward,  the  visual  axis  moves 
from  f  toward  z;  and  as  the  macula  moves  upward, 
the  visual  axis  moves  from/" toward  z '.  The  fused  point, 
/,  is  on  the  visual  axis  of  the  eye  not  under  test,  but  is  off 
the  visual  axis  of  the  ducted  eye.  In  the  duction  act  of 
fusion,  the  line  connecting-  the  fused  point  and  its  dis- 
placed imag-e  is  not  a  true  line  of  direction,  for  it  does  not 
cut  the  center  of  the  retinal  curve. 

The  existence  of  the  individual  fusion  centers  for  the 
obliques  cannot  be  proved  by  prisms,  but  the  Maddox 
rods  g-ive  positive  evidence.  With  a  triple  rod  before 
each  eye,  set  vertically,  and  with  no  prism  behind  either 
rod,  the  test  candle  will  appear  as  a  sing-le  streak  of 
lig-ht.  Turning-  the  rig-lit  rod  toward  the  temple,  with- 
in the  arc  of  possible  fusion  for  an  oblique  muscle,  will 


OF    OCULAR    ROTATIONS.  91 

not  result  in  doubling-  the  line,  but  this  doubling-  will  be 
prevented  by  the  rig-lit  7th  fusion  center  acting-  on  the 
right  inferior  oblique.  This  activity  of  center  and  muscle 
places  the  horizontal  retinal  meridian  under  the  inclined 
streak  of  lig-ht.  If  the  rig-ht  rod  had  been  turned  toward 
the  nose,  in  the  arc  of  possible  fusion  for  an  oblique  mus- 
cle, the  diplopia  would  have  been  prevented  by  the  dis- 
charg-e  of  neuricity  from  the  rig-ht  6th  fusion  center  to  the 
rig-ht  superior  oblique.  In  each  of  these  efforts  at  fusion, 
only  one  center  and  one  muscle  have  been  active.  By 
these  tests  the  existence  of  the  right  7th  and  6th  fu- 
sion centers  has  been  proved.  Leaving-  the  rig-lit  rod 
vertical  and  turning-  the  left  rod  slig-htly  out  and  in 
would  prove,  in  like  manner,  the  existence  of  the  left 
7th  and  6th  centers. 

A  final  source  of  proof  concerning-  the  existence  of  the 
four  fusion  centers  for  the  oblique  muscles  is  oblique 
astig-matism  of  one  eye,  while  the  astigmatism  of  the 
other  eye  is  either  vertical  or  horizontal.  In  the  latter 
eye  a  horizontal  line  will  have  a  horizontal  imagfe,  but  in 
the  former  eye  the  imag-e  of  the  horizontal  line  will 
be  displaced  toward  the  meridian  of  greatest  curva- 
ture, hence  this  imag-e  will  be  oblique.  To  fuse  the  ob- 
lique imag-e  with  the  one  that  is  horizontal,  an  oblique 
muscle  belong-ing-  to  the  oblique-astig-matic  e}*e,  under 
the  influence  of  the  6th  or  the  7th  fusion  center  on  the 


92  THE   FUNDAMENTAL,   PRINCIPLES 

corresponding1  side,  must  force  the  horizontal  retinal 
meridian  under  the  displaced  image.  It  would  be  the 
7th  center  and  the  inferior  oblique  if  the  most  curved 
meridian  is  in  the  upper  nasal  quadrant;  it  would  be  the 
6th  center  and  superior  oblique  if  the  meridian  of  great- 
est curvature  is  in  the  upper  temporal  arc,  whether  it  be 
the  one  eye  or  the  other. 

For  further,  and  a  more  comprehensive,  study  of  the 
ocular  muscles,  normal  and  abnormal,  from  the  brain- 
side  of  all  questions  that  can  arise,  the  reader  is  referred 
to  the  author's  other  book,  "Ophthalmic  Neuro-Myol- 
ogy,"  a  necessary  companion  volume  to  this  book.  In 
this  companion  volume  the  brain-centers,  voluntary  and 
fusion,  and  their  muscle  connections,  are  freely  and  fully 
illustrated.  The  origin,  course,  and  distribution  of  all 
the  motor  nerves  of  the  eye  are  also  fully  illustrated.  In 
all,  there  are  thirty-nine  full-page  plates,  the  reproduced 
one,  (Fig1.  15)  on  next  page,  constituting1  the  foundation 
for  all  the  others.  Besides  these  full-pag'e  cuts,  there  are 
twelve  smaller  illustrations.  The  book  contains  210 
pages  of  illustrations  and  reading  matter,  all  pertaining 
to  the  nervous  system  as  related  to  the  ocular  muscles, 
extrinsic  and  intrinsic.  In  Fig.  15  the  upper  part  rep- 
resents, schematically,  the  volitional  and  fusional  brain- 
centers — the  former  at  the  margin,  the  latter  grouped 
near  the  median  line.  All  these  centers  exist  in  dupli- 


OF    OCULAR    ROTATIONS. 


93 


3 


Fig.  15- 


94  THE   FUNDAMENTAL    PRINCIPLES 

cate,  but  the  volitional  centers  are  not  all  active.  The 
smaller  circles  at  the  periphery  represent  the  centers 
unused  by  a  right-handed  man,  only  one  of  which  is  in 
the  left  side  of  the  brain.  Conjugate  and  basal  centers 
10  and  11  belong  to  the  ciliary  body  and  iris.  While 
only  half  of  the  conjugate  centers  are  ever  used,  all  of 
the  basal  centers  stand  ready  for  action  at  the  command 
of  the  fusion  faculty  of  the  mind. 

THE    HOROPTER — MONOSCOPTER — ISOGONAL    ClRCLE. 

There  is  now  neither  mystery  nor  complicated  mathe- 
matics connected  with  the  circle  bearing  the  three  names: 
Horopter,  Monoscopter,  and  Isogonal  Circle.  The  sim- 
plicity of  this  comes  as  the  result  of  the  author's  discov- 
ery that  the  macula  is  the  posterior  pole  of  the  eye,  and 
that  the  center  of  rotation  is  the  point  of  crossing  of  all 
visual  lines.  Fig.  16  is  a  photographic  reproduction  of 
the  first  correct  horopteric  figure  ever  published,  and 
was  constructed  by  the  author  in  1892,  immediately  after 
his  discovery  of  the  true  law  of  visible  direction — viz., 
All  lines  of  direction  are  radii  of  retinal  curvature  pro- 
longed. Le  Conte,  in  "Sight,"  first  edition  (1882), 
thought  he  had  correctly  constructed  Mueller's  horopter. 
This  is  shown  in  his  reproduced  figure,  Fig.  9  (page  36), 
in  which  the  circle  is  constructed  through  the  two  cen- 
ters of  rotation  and  the  point  of  fixation;  but  he  has 


OF    OCULAR    ROTATIONS.  95 

ruined  the  figure  by  constructing1  his  indirect  visual  lines 
in  such  a  way  as  to  make  them  cross  the  visual  axes  at 
the  nodal  points.  Noyes  evidently  had  the  same  concep- 
tion of  Mueller's  horopter,  for  he  said:  "It  is  a  circle 
which  passes  through  the  center  of  rotation  of  each  eye 
and  the  point  of  fixation  of  the  visual  axes."  If  Noyes 
had  drawn  indirect  visual  lines,  he  would  have  made  them 
cross  the  visual  axes  at  the  nodal  points,  as  did  Le  Conte. 
At  any  rate,  there  was  something"  that  confused  him,  for 
he  said:  "  This  statement  is  not  strictly  correct,  but  will 
suffice  for  our  purposes."  No  horopteric  circle  is  correct 
that  does  not  make  indirect  visual  lines  cross  the  visual 
axes  at  the  center  of  rotation. 

Le  Conte,  in  his  1897  edition  of  "  Sight,"  published  a 
new  figure  which  he  claimed  as  a  true  presentation  of 
the  Mueller  horopter.  This  1897  figure  is  reproduced  in 
Fig.  10  (page  37).  This  circle  is  constructed  through 
the  two  nodal  points  and  the  point  of  fixation,  and  the 
direct  and  indirect  visual  lines  are  made  to  cross  each 
other  on  the  circle.  Le  Conte's  two  figures  as  re- 
produced in  this  chapter,  on  pages  36  and  37,  should  be 
studied  in  contrast  with  each  other.  In  Fig.  9,  the  vis- 
ual axes,  under  the  same  angle  of  convergence,  could 
move  from  point  to  point  on  the  circle,  each  eye  around 
the  point  common  to  the  visual  axis  and  the  circle;  but 
the  visual  axes  A-c  and  A-c  could  never  be  made  to  take 


96  THE    FUNDAMENTAL    PRINCIPLES 

the  place  of  the  indirect  visual  lines  B-b  and  B-b' ,  for  his 
indirect  visual  lines  do  not  cut  the  visual  axes  at  the  cen- 
ters of  rotation,  but  at  n  and  ri ,  the  so-called  nodal  points. 
It  will  be  further  observed  that  the  two  eyes  in  Fig.  9 
are  ideal  eyes  of  Helmholtz,  in  that  the  visual  axes  pass 
through  the  centers  of  rotation. 

As  erroneous  as  is  Fig-.  9,  Fig-.  10  is  still  worse.  If 
the  visual  axes  A-c  and  A-c  should  move  from  A  to  B, 
neither  eye  would  rotate  around  a  point  common  to  its 
visual  axis  and  the  horopter,  hence  the  points  n  and  n 
would  be  made  to  leave  the  circle;  or  if  the  circle  should 
move  with  the  nodal  points,  it  would  be  forced  to  leave 
the  points  A  and  B.  It  is  equally  clear  that  A-c  and 
A-c  could  never  be  made  to  take  the  positions  B-b  and 
B-b'. 

The  true  horopter,  in  the  sense  that  it  is  the  circle  of 
binocular  single  vision,  both  direct  and  indirect,  as  shown 
in  Fig-.  16,  is  based  on  three  great  facts:  (a)  The  macula 
of  all  eyes  is  the  posterior  pole,  and  the  visual  axis  is  the 
antero-posterior  axis  of  the  eye;  (b)  all  indirect  lines  of 
vision  cross  the  visual  axis  at  the  center  of  rotation;  (c) 
corresponding  retinal  points  have  a  common  brain-cell 
connection,  and  these  points  bear  identical  relationship, 
in  degrees,  to  their  respective  maculas.  In  this  figure 
the  circle  is  constructed  through  two  fixed  points  and 
one  changeable  point,  the  former  being  the  centers  of  ro- 


OP    OCULAR   ROTATIONS. 


97 


tation  of  the  eyes,  b  and  d,  and  the  latter  the  point  of 
direct  fixation.  This  circle  is  b-d-e-c-a.  Any  point  so 
situated  on  the  circle  as  to  throw  light  into  the  two  eyes 
will  be  seen  as  a  single  point,  for  the  images  will  be  on 
corresponding  retinal  points.  The  direct  point  of  view, 


Fig.  i 6. 

c,  and  its  images,  h  and  gr,  will  be  connected  by  lines 
that  cut  the  centers  of  rotation,  b  and  d.  The  secondary 
point  of  view  a  and  its  images,  /  and  /,  will  be  connected 
by  lines  passing  through  the  centers  of  rotation,  b  and 
d;  and  the  secondary  point  e  will  be  connected  with  its 
images,  /  and  k,  by  lines  that  cut  the  visual  axes  at  the 


98  THE   FUNDAMENTAL,   PRINCIPLES 

centers  of  rotation.  That  all  points  on  this  circle,  whether 
direct  or  indirect,  will  be  seen  under  the  same  angle, 
is  proved  by  the  fact  that  each  angle  is  measured  by  half 
the  arc  b-d,  for  each  is  an  inscribed  angle,  with  this  com- 
mon arc.  If  the  visual  axes  should  be  moved  from  c  to  «, 
they  will  take  the  positions  of  the  indirect  visual  lines,  a-j 
and  a-f;  if  the  visual  axes  should  be  moved  from  c  to  e, 
they  will  take  the  positions  of  the  indirect  lines,  e-l  and 
e-k.  The  figure  also  shows  that  the  direct  and  the  indi- 
rect points  of  view  are  related  in  degrees  as  are  their  re- 
spective images.  The  angle  c-b-a  is  an  inscribed  angle 
and  is  measured  by  half  the  arc  a-c.  The  angle  h-b-j  is 
an  angle  at  the  center  and  is  measured  by  the  whole  arc 
h-j.  But  these  angles  are  opposite  and  are,  therefore, 
equal.  The  angle  a-d-c  is  equal  to  the  angle  a-b-c,  for 
it,  too,  is  measured  by  half  the  same  arc,  a-c;  therefore 
the  angle g'-d-f  is  equal  to  the  angle  h-b-j.  Since/ and  f 
are  similarly  related,  in  degrees,  to  the  maculas,  ^and^, 
they  are  corresponding  retinal  points,  for  such  points 
have  common  brain-cell  connection.  The  statements 
made  above  are  strictly  correct,  and,  therefore,  Fig.  16 
TV  ill  suffice  for  all  purposes  in  the  study  of  binocular  sin- 
gle vision  and  binocular  rotations. 

Points  on  the  circle  whose  indirect  visual  lines  cross 
m-a  at  the  same  point  are  equally  far  removed  from  the 
direct  point  of  view.  To  show  this,  the  line  m-c  was 


OF    OCULAR    ROTATIONS.  99 

drawn.  For  a  different  purpose  entirely,  and  one  more 
practical,  the  line  b-d  was  placed  in  the  figure. 

Having1  demonstrated  the  curved  line  of  binocular  sin- 
gle vision,  it  was  only  one  step  to  the  demonstration  of 
the  curved  surface  of  binocular  single  vision.  The  au- 
thor suggested  to  Dr.  Manning-  Brown,  now  of  Hopkins- 
ville,  Ky.,  then  his  private  student,  that  this  surface 
could  be  generated  by  revolving-  the  circular  plane, 
b-d-e-c-a,  on  the  cord,  b-d.  Dr.  Brown  at  once  volun- 
teered to  have  this  peculiar  surface  of  single  seeing-  made 
in  wood,  by  means  of  the  skillful  use  of  the  turning- 
lathe.  This  he  succeeded  in  doing-.  This  oddly,  but 
beautifully,  shaped  piece  of  wood  was  then  cut  along- 
a  plane  including-  the  line  b-d,  into  two  equal  parts,  with 
a  very  delicate  saw.  E}ach  of  the  two  cut  surfaces  pre- 
sented a  plane  the  outlines  of  which  were  larg-e  seg-ments 
of  two  circles,  as  shown  in  Fig-.  17,  which  represents  a 
vertical  section  of  this  model. 

It  is  clear  that  the  parts  above  and  below  b-d  are  pre- 
cisely alike.  In  this  figure,  b  and  d  represent  the  cen- 
ters of  the  two  eyes,  and  b-d  is  the  line  connecting- 
these  centers.  The  circular  planes  shown  on  either  side 
of  b-d,  each  represents  perfectly  the  plane  of  the  horop- 
ter.  A  section  made  from  any  point  on  the  surface  of 
this  model,  along-  a  plane  including-  the  line  b-d,  would 
have  shown  the  two  conjoined  horopteric  planes  just  as 


100 


THE  FUNDAMENTAL  PRINCIPLES 


Fig.  17. 


OF    OCULAR   ROTATIONS.  101 

depicted  in  Fig.  17.  As  on  the  line,  so  on  the  surface 
generated,  there  is  not  a  point  so  situated  as  to  send  light 
into  the  two  eyes  but  that  it  would  be  seen  as  a  single 
point  with  the  two  eyes.  The  concave  area  of  binocular 
single  seeing  is  clearly  shown  in  Fig.  25. 

The  section  of  this  model  should  have  led  at  cnce  to 
the  making  of  Fig.  18,  but,  in  fact,  it  was  fifteen  years 
later  (1907)  before  the  author  found  the  artist  who  could 
make  this  complicated  figure,  to  be  studied  further  on. 

Referring  again  to  Fig.  16,  it  may  be  stated  that,  since 
b-a-c-e-d  is  the  line  of  binocular  single  vision,  all  points 
within  and  beyond  it  should  be  seen  double.  This  is  lit- 
erally true  as  applied  to  small  circles;  and  it  is  alwa}Ts 
true  as  to  near-by  points,  however  large  the  circle  may 
be.  If  the  horopteric  circle  has  a  diameter  of  thirty  feet, 
objects  beyond  will  not  appear  as  double,  though  points, 
if  they  could  be  seen  so  far,  would  be  double.  Even  the 
double  appearance  of  near-by  objects,  when  the  circle  is 
small  or  large,  is  not  confusing,  nor  is  it  hurtful,  for  no 
attempt  is  made  by  the  mind  or  eyes  to  fuse  such  images. 

In  1898,  Maddox  published  in  his  book,  "  The  Ocular 
Muscles,"  a  cut  which  he  named  the  "  Isogonal  Circle." 
This  circle  he  constructed  through  the  centers  of  rotation 
and  the  point  of  fixation.  In  the  cut  he  had  no  indirect 
visual  lines,  but  only  the  two  visual  axes,  converged  first 
on  the  direct  point  on  the  circle,  and  then  rotated  to  a  sec- 


102  THE   FUNDAMENTAL   PRINCIPLES 

ondary  point.  His  purpose  was  to  show  that  the  angle 
of  conversance  was  the  same  for  the  two  points.  If  he 
had  seen,  he  had  not  accepted,  the  teaching  of  the  au- 
thor that  all  points  on  this  circle,  whether  direct  or  indi- 
rect, were  seen  as  single  points  and  under  a  common  an- 
gle. The  author,  some  years  before,  had  named  Fig.  16 
"the  monoscopter, "  the  meaning  of  which  is  "line  of 
binocular  single  vision."  Either  one  of  the  names  is  bet- 
ter than  the  older  name,  "  horopter,"  which  means  "  the 
limit  of  seeing."  Since  points,  to  be  seen  as  single,  must 
be  seen  under  the  same  angle,  and  for  other  reasons,  the 
name  " isogonal  circle "  is  preferable  to  the  name  "mono- 
scopter." The  name  "isogonal  circle  "  may  be  defined 
as  follows:  The  circle  on  which  all  visual  lines,  lying  in 
a  common  plane  and  coming  from  corresponding  retinal 
points,  converge,  each  two  lines  forming  the  same  angle 
as  do  all  other  two  lines.  This  has  been  shown  to  be  true 
in  the  study  of  Pig.  16.  The  name  "  isogonal  "  may  be 
made  to  apply  to  the  surface  of  single  seeing  as  well  as 
to  the  circle.  ' '  Isogonal  surface ' '  may  be  defined  as  fol- 
lows: The  two  visual  lines,  whether  direct  or  indirect, 
from  corresponding  retinal  points,  converging  at  any 
point  on  this  surface,  form  the  same  angle  as  the  two  vis- 
ual lines  converging  at  any  other  point  on  this  surface. 

The  definition  of  the  isogonal  circle  as  given  by  Mad- 
dox,  in  connection  with  his  figure  of  the  circle  constructed 


OF    OCULAR    ROTATIONS. 


103 


through  the  centers  of  rotation  and  the  point  of  fixation, 
is  as  follows:  "  It  is  the  curve  of  uniform  convergences 
and  of  equal  lateral  ductions  for  the  two  eyes." 

c' 


M 

Fig.  i 8. 

In  the  study  of  Fig1.  18,  published  for  the  first  time  in 
1907,  the  author  accepts  the  name  "  isogonal  circle  "  in 
its  fuller  meaning,  in  preference  to  either  of  the  two 
other  names — "  horopter  "  and  "monoscopter."  Equal 


104  THE    FUNDAMENTAL    PRINCIPLES 

angles  of  all  two  visual  lines  from  corresponding-  retinal 
points  on  a  circle  (isogonal)  means  binocular  single  vi- 
sion; binocular  single  vision  of  points  on  a  circle  (mono- 
scopteric)  means  equal  angles.  Since  the  two  terms 
mean  practically  the  same  thing,  "isogonal"  has  the 
preference  over  "  monoscopteric "  when  joined  with 
"circle,"  because  it  is  more  easily  pronounced  and  is 
more  pleasing  to  both  the  ear  and  the  eye. 

The  spherical  concavity  of  the  retinas,  corresponding 
retinal  points,  and  the  law  of  visible  direction,  make  pos- 
sible the  mathematical  circle  and  surface  of  binocular 
single  vision.  In  the  light  of  Fig.  18,  the  isogonal  circles 
will  be  studied  as  belonging  to  one  of  two  classes.  To 
the  first  class  belongs  only  one  circle,  and  there  is  no  bet- 
ter way  to  distinguish  it  from  the  many  members  of  the 
other  class,  than  by  naming  it  the  Primary  Isogonal  Cir- 
cle. The  circles  of  the  other  class  should  be  known  as 
Secondary  Isogonal  Circles. 

THE  PRIMARY  ISOGONAL  CIRCLE. — In  Fig.  18,  M-C 
represents  the  extended  median  plane  of  the  head,  and  C 
is  a  point  on  the  line  of  intersection  of  this  plane  and  the 
horizontal  plane  of  the  head.  With  C  as  the  point  of 
fixation,  the  primary  isogonal  circle  must  pass  through 
it.  The  other  two  points  through  which  this  circle  must 
pass  are  the  centers  of  rotation  of  the  two  eyes,  D  and  B. 
The  primary  isogonal  circle,  B-D-C,  thus  constructed, 


OF    OCULAR    ROTATIONS.  105 

presupposes  that  both  the  head  and  the  eyes  are  in  their 
primary  positions.  The  distinguishing  fact  of  this  circle 
is  that  in  its  plane  lie  the  two  visual  axes  and  the  two 
horizontal  retinal  meridians,  and  that  the  visual  axes  are 
converged  to  a  point  on  it.  On  either  side  of  the  point 
of  fixation  are  many  indirect  points  of  view  on  this  circle, 
and  in  its  plane  lie  twice  as  many  indirect  lines  of  vision, 
for  to  each  point  belong  two  lines. 

THE  SECONDARY  ISOGONAL,  CIRCLES  are  constructed 
through  the  two  centers  of  rotation,  B  and  D,  and 
through  indirect  points  of  view  lying  in  the  extended 
vertical  plane  of  the  head,  both  above  and  below  C,  each 
and  all  of  these  points  being  the  same  distance  from  the 
point  of  intersection  of  M-C  and  B-D  as  is  the  point  C. 
Fig.  18  shows  only  one  of  these  secondary  circles,  B-D-C '. 
Lying  on  this  circle — to  either  side  of  C',  itself  a  second- 
ary point — are  many  other  secondary  points,  as  E.  Each 
of  these  secondary  circles  has  on  it  only  secondary  points 
of  view,  and  in  its  plane  lie  only  indirect  visual  lines,  two 
for  each  point.  The  plane  of  no  secondary  isogonal  cir- 
cle contains  a  retinal  meridian,  but  it  intersects  the 
planes  of  all  the  retinal  meridians.  The  number  of  sec- 
ondary isogonal  circles  can  be  computed  if  they  should  be 
considered  as  only  1"  apart.  By  reference  to  Fig.  24,  it 
will  be  seen  that  the  upper  part  of  the  field  of  binocular 
single  vision  is  55°  and  the  lower  part  of  this  field  is  70°. 


106  THE   FUNDAMENTAL   PRINCIPLES 

This  would  give  198,000  secondary  isogonal  circles  above 
the  primary  circle,  and  252,000  below  it,  making-  a  total  of 
450,000  secondary  isogonal  circles  to  one  primary  isogo- 
nal  circle. 

All  isogonal  circles,  whether  primary  or  secondary,  are 
alike  in  the  following  respects:  (a)  They  are  all  con- 
structed through  two  common  points,  the  centers  of  ro- 
tation, B  and  Z?,  of  the  two  eyes;  (b)  they  all  have  a 
common  cord  (J3-D],  the  lines  connecting  the  centers  of 
the  two  eyes;  (c)  they  are  all  bisected  b}r  the  extended 
median  plane  of  the  head;  (d)  all  points  on  all  of  the  cir- 
cles, belonging  to  one  group,  so  located  as  to  send  light 
into  the  two  eyes,  will  be  seen  as  single  points;  (e)  the 
two  lines  of  vision  connecting  any  secondary  point,  on 
any  circle  of  a  given  group,  with  its  two  images,  have 
the  same  angle  as  that  formed  by  the  convergence  of 
the  visual  axes  on  the  point  of  direct  view — the  angles 
B-A-D,  B-C'-D,  and  B-E-D  are  equal  to  the  angle 
B-C-D. 

What  has  been  said  above  in  (a),  (b),  and  (c)  applies  to 
all  circles  of  all  groups.  What  has  been  said  in  (d) 
and  (e)  applies  to  any  single  group  of  isogonal  circles 
— circles  that  have  the  same  diameter.  An  infinite  num- 
ber of  points  lie  on  the  line  of  intersection  of  the  extended 
vertical  and  horizontal  planes  of  the  head,  and  each  of 
these  points  may  become  the  primary  point  of  view — the 


OF    OCULAR    ROTATIONS.  107 

point  of  direct  fixation.  For  each  of  these  points  there  is 
a  possible  primary  isogonal  circle;  hence  the  number  of 
possible  primary  isogonal  circles  is  infinite,  but  only  one 
can  exist  at  a  time.  Each  new  primary  isogonal  circle 
creates  a  new  group  of  secondary  circles,  all  of  equal 
size. 

There  is  no  point  in  the  space  devoted  to  binocular  sin- 
gle vision  (see  Fig1.  24)  that  does  not  lie  on  some  isogonal 
circle,  or  in  the  plane  of  one  of  these  circles.  The  field 
of  binocular  rotations  is  a  little  smaller  than  the  field  of 
binocular  single  vision,  but  any  secondary  point  within 
this  smaller  field  may  become  the  point  of  fixation,  and 
that,  too,  regardless  of  the  size  of  the  circle  on  which 
the  secondary  point  may  be  located. 

The  degree  of  convergence  of  the  visual  axes  at  a  sec- 
ondary point  will  be  the  same  as  if  they  were  converged 
on  the  direct  point  of  that  primary  circle  which  belongs 
to  the  same  group.  This  is  well  shown  in  Fig.  18,  in 
which  the  visual  axes  can  be  considered  as  moved,  first 
from  C  to  C',  and  again  from  C'  to  E.  In  either  case 
the  visual  axes  have  been  made  to  take  the  position  of 
indirect  visual  lines,  under  the  same  angle  of  convergence. 

If  the  point  for  indirect  fixation  is  on  a  smaller  or  lar- 
ger circle  than  is  the  primary  point  of  view,  the  primary 
circle,  which  must  move  with  the  visual  axes,  must  grow 
smaller  or  larger  until  it  shall  finally  include  the  second- 


108  THE    FUNDAMENTAL    PRINCIPLES 

ary  point  to  be  fixed.  If,  at  the  beginning-  of  a  rotation, 
the  second  point  of  view  lies  on  the  circumference  of  the 
primary  isogonal  circle,  that  circle  neither  enlarges  nor 
does  its  plane  move,  while  the  visual  axes  move  from  one 
point  of  view  to  the  other.  If  the  second  point  of  view 
is  at  a  greater  distance  than  the  first  point,  but  in  the 
plane  with  it,  the  circle  enlarges,  but  the  plane  does  not 
move,  as  the  visual  axes  pass  from  the  one  point  to  the 
other.  If  the  second  point  of  view  is  in  the  plane  of  a 
secondary  isogonal  circle,  the  plane  of  the  primary  circle 
moves  into  the  position  of  the  secondary  circle  as  the  vis- 
ual axes  converge  on  the  second  point.  No  point  in 
viewable  space  can  be  fixed  until  the  plane  of  the  pri- 
mary isogonal  circle  is  made  to  include  it,  as  the  visual 
axes  converge  upon  it. 

From  the  foregoing  it  will  be  seen  that  the  plane  of  all 
isogonal  circles  are  movable  planes,  and  that  the  common 
axis  around  which  they  rotate  is  the  line  connecting  the 
centers  of  the  two  eyes — the  line  B-D  in  Fig.  18.  If  the 
visual  axes  rise,  the  primary  isogonal  rises  with  them;  if 
the  visual  axes  must  be  depressed,  the  primary  isogonal 
circle  must  go  down  with  them.  As  the  primar}T  isogo- 
nal circle  rotates,  all  secondary  isogonal  circles  rotate 
with  it,  in  the  same  direction  and  to  the  same  extent. 
Thus  within  the  limit  of  vertical  rotations,  the  plane  of 
the  primary  circle  may  be  made  to  assume  the  former 


OF   OCUL,AR   ROTATIONS.  109 

position  of  the  plane  of  any  secondary  circle.  As  the 
plane  of  the  primary  circle  rises  or  falls,  the  visual  axes 
move  in  the  moving-  plane,  if  the  second  point  is  obliquely 
located,  so  as  to  converge  on  the  second  point  of  view  at 
the  moment  that  the  plane  reaches  that  point.  In  doing 
this  the  point  of  convergence  moves  along  a  binocular 
spacial  meridian.  (See  Fig.  25.) 

THE  LAW  OF  BINOCULAR  REST  AND  MOTION. 

THE  TWELVE  EXTRINSIC  MUSCLES  OF  NORMAL  EYES, 
UNDER  THE  CONTROL  OF  THE  NINE  CONJUGATE,  AND 
THE  TWELVE  FUSION,  BRAIN-CENTERS,  MUST  SO  RE- 
LATE THE  TWO  EYES  THAT  THEIR  TWO  VISUAL  AXES 
AND  THE  TWO  HORIZONTAL  RETINAL  MERIDIANS  SHALL 
ALWAYS  LIE  IN  THE  PLANE  OF  THE  PRIMARY  ISOGONAL 
CIRCLE,  WHETHER  AT  REST  OR  IN  MOTION,  AND  THAT 
THE  TWO  VISUAL  AXES  SHALL  CONVERGE  AT  SOME 
POINT  ON  THIS  CIRCLE,  IN  THE  INTEREST  OF  BOTH  BIN- 
OCULAR SINGLE  VISION  AND  CORRECT  ORIENTATION. 

The  two  eyes,  while  obeying  the  law  of  binocular  ro- 
tation, do  not  violate  the  law  of  monocular  motion.  Each 
visual  axis  moves  in  the  plane  of  that  individual  retinal 
meridian  projected  into  space,  on  which  lie  both  the  first 
and  the  second  points  of  view,  during  which  motion  the 
vertical  axis  of  the  eye  will  be  kept  parallel  with  the 
median  plane  of  the  head.  The  fusion  centers,  not  used 


110  THE    FUNDAMENTAL    PRINCIPLES 

in  monocular  rotations,  are  essential  in  binocular  rota- 
tions. Without  the  fusion  centers,  even  when  muscles 
are  normal  in  tone,  all  oblique  rotations  would  be  at- 
tended by  diplopia;  and  without  them,  muscles  of  unequal 
tonicity  would  cause  diplopia,  whether  the  e}res  be  at  rest 
or  in  motion,  as  shown  in  the  study  of  Fig-.  14. 

The  cord  common  to  all  isog-onal  circles — the  line,  JB-D, 
connecting1  the  centers  of  the  two  eyes — should  always 
lie  in  the  horizontal  plane  of  the  head;  but  this  cannot 
be  if  one  eye  is  set  lower  in  the  orbit  than  is  the  other. 
Even  in  such  faulty  eyes  the  horizontal  retinal  meridians 
must  lie  in  the  plane  of  the  laterally  inclined  primary  isog-- 
onal  circle,  when  both  eyes  are  being1  used.  Should  the 
plane  be  inclined  5°,  the  vertical  axes  of  the  two  eyes  must 
be  inclined  throug-h  the  same  arc,  toward  the  side  of  the 
lower  eye.  This  would  be  effected  by  activity  of  either 
the  8th  or  9th  conjugate  center,  on  the  superior  oblique 
of  one  eye  and  the  inferior  oblique  of  the  other.  With  one 
eye  covered,  as  in  the  work  of  refraction,  the  con  jug-ate  cen- 
ter would  cease  its  activity  and  the  eye  would  then  have 
its  vertical  axis  normally  related  to  the  median  plane  of 
the  head.  On  uncovering-  the  eye,  the  two  vertical  axes 
would  be  tilted  ag-ain  toward  the  side  of  the  lower  eye. 
The  practical  point  growing-  out  of  this  observation  is 
that  such  eyes  would  require  the  shifting-  of  the  axes  of 
correcting-  cylinders  toward  the  side  of  the  lower  eye, 


OF    OCULAR    ROTATIONS.  Ill 

through  arcs  corresponding-  to  the  lateral  displacement 
of  the  horizontal  retinal  meridians. 

In  the  interest  of  binocular  single  vision,  but  against 
correct  orientation,  the  horizontal  retinal  meridians  of 
uncorrected  oblique  astigmatic  eyes  must  be  forced  out 
of  the  plane  of  the  primary  isogonal  circle.  This  sub- 
ject will  be  given  proper  emphasis  in  the  chapter  on 
"Compensating  Cyclotropia."  In  that  chapter  the  6th 
and  7th  conjugate  centers  are  represented,  respectively, 
as  the  source  of  power  for  converging  and  diverging  the 
vertical  axes  of  the  eyes  in  the  interest  of  fusion  of  dis- 
placed images.  It  probably  would  be  more  nearly  cor- 
rect to  say  that  this  work  is  accomplished  by  the  right 
and  left  6th,  and  the  right  and  left  7th,  basal  centers,  as 
has  been  pointed  out  in  the  study  of  Fig.  14.  The  fusion 
function  must  be  under  the  control  of  the  fusion  faculty 
of  the  mind,  and  this  faculty  presides  over  the  single 
basal  centers,  right  and  left. 

Emmetropia  and  orthophoria  make  it  easy  for  the  ocu- 
lar muscles  to  obey  the  law  of  binocular  rotation.  Hy- 
peropia  and  myopia  interfere  with  the  act  of  convergence; 
oblique  astigmatism,  with  meridians  of  greatest  curva- 
ture diverging  or  converging,  makes  it  impossible  for  the 
obliques  to  keep  the  horizontal  retinal  meridians  in  the 
plane  of  the  primary  isogonal  circle;  hyperphoria  and 
cataphoria  make  it  hard  for  the  superior  and  inferior 


112  THE    FUNDAMENTAL    PRINCIPLES 

recti  to  plane  the  visual  axes;  exophoria  and  esophoria 
make  difficult  the  task  of  converging  the  visual  axes  to 
points  on  the  circle,  and  the  shifting  of  the  visual  axes  in 


Fig.   19. 

the    plane    of  the    circle,   by   the    lateral   recti.     In  the 
light  of  these  facts,  it  would  appear  that  the  e}Tes,  not  nat- 


OF    OCULAR    ROTATIONS.  113 

urally  so,   should  be  made  emmetropic  and  orthophoric 
by  art. 

THE  MUSCLE  INDICATOR. — This  device  is  the  primary 
isogonal  circle  put  in  material  form,  as  shown  in  the 
half-tone  picture,  Fig-.  19.  The  circle  o-M-N-o  passes 
through  the  centers  of  rotation,  o  and  o,  and  through 
the  direct  point  of  fixation,  shown  at  the  intersection 
of  the  visual  axes.  The  horizontal  retinal  meridians  are 
represented  by  the  two  circles,  E  and  E,  each  passing- 
through  two  vertical  slots,  S  and  S.  They  both  lie  in 
the  plane  of  the  larg-er  circle,  and  each  is  supported  in 
that  position  by  the  two  clips,  C  and  C.  Each  visual 
axis,  V-A,  extends  from  the  macula  at  E,  throug-h  the  cen- 
ter of  rotation,  o,  on  through  the  cornea,  either  at  or 
near  its  center,  thence  across  the  circle  to  meet  its  fel- 
low-axis at  the  point  on  the  circle  through  which  passes 
the  extended  median  plane  of  the  head.  The  two  visual 
axes,  as  well  as  the  two  horizontal  retinal  meridians,  are 
lying  in  the  plane  of  the  circle.  The  clips,  C  and  C, 
across  the  front  vertical  slot,  S,  prevent  the  visual  axes 
from  rising  above  or  falling  below  this  plane.  Each  vis- 
ual axis  is  made  of  two  pieces  of  copper  wire  and  a  tube, 
so  as  to  make  both  lengthening  and  shortening  possible, 
as  the  point  of  view  may  be  changed.  The  horizontal 
slot,  M-N,  allows  the  moving  of  the  point  of  fixation  of 
the  visual  axes  both  to  the  left  and  to  the  right.  The 
slot,  M-N,  does  not  quite  reach  the- limit  of  lateral  rota- 


114  THE   FUNDAMENTAL    PRINCIPLES 

tions,  but  it  extends  far  enough  to  show  how  the  visual 
axes  can  be  made  to  move  in  the  plane  of  the  circle, 
around  the  centers  of  rotation,  o  and  o.  The  circle  is 
supported  by  the  upright,  U,  attached  to  the  base,  B. 
At  the  upper  end  of  the  upright  there  is  a  screw  attach- 
ment for  either  fixing  the  circle  in  the  horizontal  posi- 
tion, or  allowing  it  to  rotate  up  or  down,  on  the  cord,  o-o, 
the  line  that  connects  the  centers  of  the  two  eyes.  The 
screw  is  worked  by  the  sliding  rod,  R-R.  Imagining 
that  the  real  circle  in  Fig.  19  has  a  diameter  of  twenty 
feet,  then  it  will  not  be  hard  to  conceive  that  the  tonicity 
of  the  superior  and  inferior  recti  has  planed  the  visual 
axes,  and  that  tonicity  of  the  lateral  recti  has  converged 
them;  nor  will  it  be  a  difficult  matter  to  understand  that 
the  tonicity  of  the  superior  and  inferior  obliques  has 
planed  the  horizontal  retinal  meridians.  The  clips,  C 
and  C,  front  slot,  S,  represent  the  power  that  keeps 
the  visual  axes  planed,  and  that  power  resides  in  the 
superior  and  inferior  recti.  The  four  clips,  C,  across 
the  vertical  slots  through  which  the  horizontal  meridians 
pass,  represent  the  power  that  planes  these  meridians, 
and  this  power  resides  in  the  superior  and  inferior  ob- 
liques. When  the  tonicity  of  either  of  these  pairs  of 
muscles  is  unequal,  the  planing  of  the  visual  axes  or  the 
horizontal  retinal  meridians,  as  the  case  may  be,  can  be 
maintained  only  by  contractility  of  the  weaker  muscle  of 


OF    OCULAR    ROTATIONS.  115 

a  pair.  Should  the  lateral  recti  muscles  be  unequal  in 
tone,  the  visual  axes  would  tend  to  cross,  either  within 
or  beyond  the  circle,  and  only  contractility  of  the  weaker 
muscle  of  each  pair  would  compel  them  to  converge  on 
the  direct  point  of  view. 

If  tonicity  keeps  the  horizontal  retinal  meridians  and 
visual  axes  in  the  plane  of  the  primary  isogonal  circle, 
when  lying  in  the  horizontal  plane  of  the  head,  and  con- 
verges these  axes  at  the  direct  point  of  view  on  this  cir- 
cle, the  rotations  will  all  be  effected  by  the  normal  ex- 
penditure of  neuricity.  That  the  visual  axes,  when  ro- 
tated from  any  one  point  of  view  to  any  other  point  of 
view,  assume  the  exact  positions  of  the  two  indirect  vis- 
ual lines  which  connected  the  second  point  of  view  and  its 
two  images,  before  the  rotation  began,  can  easily  be 
shown  by  a  further  study  of  Fig.  19,  in  connection  with 
a  glance  at  Fig.  20.  Before  rotating  the  visual  axes 
from  the  primary  point,  shown  in  Fig.  19,  to  the  sec- 
ondary point,  TV,  directly  to  the  right,  two  wires  should 
be  made  to  extend  from  TV,  directly  over  the  right  end  of 
the  horizontal  slot,  J/-TV,  the  one  wire  back  to  the  right 
retina  and  the  other  back  to  the  left  retina,  each  passing 
over  the  center  of  rotation,  o,  of  its  eye.  These  wires 
should  be  firmly  held  in  their  respective  positions  while 
the  visual  axes  are  rotated  from  the  direct  point  of  view 
to  TV,  as  shown  in  Fig.  20.  At  the  end  of  the  rotation  it 


116 


THE  FUNDAMENTAL  PRINCIPLES 


will  be  found  that  the  two  visual  axes  lie  directly  under 
the  two  wires  which  were  made  to  represent  the  two  indi- 
rect visual  lines. 


Fig.  20. 

If  each  of  the  two  wires  representing-  indirect  visual 
lines,  going  from  TV,  were  carried  over  the  nodal  point 


OF    OCUIvAR    ROTATIONS.  117 

of  its  eye,  back  to  a  point  directly  above  the  supposed 
location  of  the  image  on  its  retina,  and  these  wires 
should  be  firmly  held  while  the  visual  axes  are  rotated 
from  the  direct  point  to  JV,  it  would  be  seen  that  the  vis- 
ual axes  do  not  lie  directly  under  these  wires  thus  placed. 
This  would  show  that,  while  the  two  visual  axes  have 
reached  the  second  point  of  view,  the  maculas  have  fallen 
short  of  the  two  supposed  images  of  that  point.  No  man 
can  make  these  two  experiments  with  the  Muscle  Indica- 
tor and  not  be  convinced  that  all  lines  of  direction  are 
radii  of  retinal  curvature  prolonged. 

Fig.  20  shows  that  when  the  second  point  of  view  al- 
ready lies  on  the  primary  isogonal  circle,  the  visual  axes 
move  from  the  primary  point,  in  the  plane  of  that  circle, 
but  the  circle  itself  remains  stationary. 

Fig.  21  shows  that  when  the  second  point  of  view  is 
in  the  vertical  plane  above  the  primary  point  of  view, 
the  visual  axes  are  carried  upward  in  the  rotating  plane 
of  the  primary  isogonal  circle,  without  change  of  posi- 
tion in  that  plane,  to  the  second  point  of  view.  The  pri- 
mary circle  has  been  made  to  take  the  position  of  that 
secondary  circle  on  which  rested  the  second  point  before 
the  rotation  began,  and  the  visual  axes  have  been  made 
to  assume  the  positions  of  the  two  indirect  visual  lines 
which  connected  the  second  point  and  its  two  images  be- 
fore the  rotation  started. 


118  THE    FUNDAMENTAL   PRINCIPLES 

In  both  Figs.  20  and  21,  the  point  of  convergence  of 
the  visual  axes  has  moved  along  that  binocular  spacial 
meridian  on  which  were  lying  both  the  first  and  second 


Fig.  21. 

points  of  view.     In  the  two  cardinal  directions  right  and 
left,  the  visual  axes  must  move  in  a  motionless  plane;  in 


OF    OCULAR    ROTATIONS.  119 

the  two  cardinal  directions  up  and  down,  the  visual 
axes  must  remain  motionless  in  the  moving1  plane 
throughout  the  rotation.  The  rotations  shown  in  Fig's. 
20  and  21  have  been  accomplished  without  either  the  hor- 
izontal retinal  meridians  or  the  two  visual  axes  leaving 
the  plane  of  the  primary  isogonal  circle,  and  the  visual 
axes  are  still  converged  at  a  point  on  the  circle.  The 
rotation  shown  in  Fig1.  20  has  been  effected  around  the 
vertical  axis  of  the  eye,  a  fixed  axis  throughout  the  ro- 
tation. That  shown  in  Fig.  21  has  been  accomplished 
around  the  transverse  or  horizontal  axis  of  the  eye,  like- 
wise a  fixed  axis  for  that  rotation.  In  both  of  these  ro- 
tations each  eye  has  obeyed  the  law  of  monocular  rota- 
tion, and  the  two  eyes  together  have  obeyed  the  law  of 
binocular  rotation. 

Fig.  22  shows  a  rotation  that  has  been  effected  from 
the  primary  point  of  view,  as  shown  in  Fig.  19,  to  a  sec- 
ond point  of  view  obliquely  up-and-to-the-right.  The 
primary  isogonal  circle  has  been  so  elevated  as  to  take 
the  place  of  that  secondary  circle  on  which  rested  the 
second  point  of  view  before  the  rotation  began;  and  the 
visual  axes  have  been  made  to  assume  the  position  of  the 
two  indirect  visual  lines  which  connected  that  second 
point  with  its  two  images  while  the  eyes  were  yet  fixed 
on  the  first  point.  To  fix  this  obliquely  placed  second 
point  of  view,  the  visual  axes  must  rise  with  the  plane, 


120 


THE  FUNDAMENTAL  PRINCIPLES 


and  must  move  in  this  plane  to  the  right,  as  it  ascends, 
so  as  to  converge  at  the  second  point  the  moment  the 
plane  reaches  it.  In  this  motion  with  the  plane  and  the 


Fig.  22. 

other  movement  in  the  plane,  the  point  of  convergence  of 
the  visual  axes  has  moved  along  that  binocular  spacial 


OP    OCULAR    ROTATIONS.  121 

meridian  on  which  were  lying-  both  the  first  and  second 
points  of  view. 

Pig1.  22  shows  that  this  oblique  rotation  has  been  ac- 
complished with  the  horizontal  retinal  meridians  still 
tying-  in  the  plane  of  the  primar}T  isog-onal  circle;  and  it  also 
shows  that  the  visual  axes  have  remained  in  that  plane 
and  are  converged  at  the  proper  point  on  the  circle.  The 
plane  of  the  primary  isog-onal  circle  has  been  carried  up- 
ward with  the  visual  axes  of  the  two  eyes,  which  have 
been  rotated,  each  around  its  transverse  axis,  and  the 
visual  axes  have  been  moved  in  the  slot  toward  JV  by 
an  accompanying-  rotation  of  each  eye  around  its  ver- 
tical axis.  Each  of  these  axes,  the  vertical  and  the 
transverse,  have  been  themselves  in  motion  throughout 
the  oblique  rotation.  The  perfectness  of  this  double  ro- 
tation about  the  two  moving-  axes  has  been  made  possi- 
ble by  the  obliques  preventing-  any  rotation  of  either  e}Te 
around  its  visual  axis.  The  clips  supporting-  the  two 
horizontal  retinal  meridians  show  that  these  meridians 
have  not  been  allowed  to  leave  the  moving-  plane  of  the 
primary  circle.  Fig1.  22  is  representative  of  all  oblique 
rotations. 

In  oblique,  as  in  cardinal,  rotations,  as  illustrated, 
each  eye  has  obeyed  the  law  of  monocular  rotation,  and 
the  two  tog-ether  have  obeyed  the  law  of  binocular  ro- 
tation. 


122  THE   FUNDAMENTAL,    PRINCIPLES 

If  the  oblique  rotation,  illustrated  in  Fig.  22,  had 
been  effected  around  fixed  axes,  at  right-angles  to  their 
respective  rotation  planes,  the  horizontal  retinal  merid- 


Fig.  23. 

ians  would  have  been  made  to  leave  the  plane  of  the  pri- 
mary isogonal  circle,  each  tilting-  down-and-to-the-right, 


OF    OCULAR    ROTATIONS.  123 

as  shown  in  Fig.  23,  introduced  here  to  show  ivhat  docs 
not  occur  in  any  oblique  rotation.  Two  clips  are  down. 

The  Muscle  Indicator  proves  the  existence  of  corre- 
sponding- points,  in  that  it  would  not  be  a  possibility  if 
there  were  no  such  points.  It  proves  the  correctness  of 
the  law  of  direction,  as  discovered  by  the  author — viz.: 
All  lines  of  direction  are  radii  of  retinal  curvature  pro- 
longed; for  if  this  were  not  the  true  law  of  direction, 
the  Muscle  Indicator  could  not  have  been  made.  It  proves 
that  the  macula  is  the  posterior  pole  of  the  eye;  for  if 
this  were  not  true,  the  Muscle  Indicator  would  be  a  mus- 
cle mystifier.  Of  a  muscle  mystifier  this  could  not  be 
said:  "  There  is  not  a  single  phase  of  a  single  ocular 
muscle,  or  any  combination  of  ocular  muscles,  normal, 
abnormal,  or  pathological,  which  the  Muscle  Indicator 
will  not  show."  It  is  the  embodiment  of  truth,  con- 
densed and  clarified,  concerning  all  muscle  problems. 
With  its  aid  the  mediocre  mind  may  become  master  of 
muscle  questions  which  were  baffling  to  the  brightest 
intellects  of  other  days.  It  is  the  only  device  that 
teaches  "the  truth,  the  whole  truth,  and  nothing  but 
the  truth,"  concerning  binocular  rest  and  easy  motions 
of  orthophoric  eyes,  and  concerning  binocular  unrest  and 
uneasy  rotations  of  heterophoric  eyes. 

In  an  early  part  of  this  chapter,  Figs.  3  and  4  were 
introduced  to  make  easier  the  study  of  monocular  motion. 


124 


THE;  FUNDAMENTAL  PRINCIPLES 


OF    OCULAR    ROTATIONS.  125 

These  two  figures  are  so  familiar  to  all  readers,  having 
been  seen  in  practically  all  books  on  the  eye,  it  would 
seem  superfluous  to  sa}T  anything-  more  about  them.  In 
other  books,  however,  Figs.  3  and  4  only  represented 
the  field  of  vision  for  the  left  and  the  right  eyes  respec- 
tively, as  shown  within  the  shadings  above,  below,  and 
to  the  inner  side.  Heretofore  the  lines  traversing  the 
white  space  were  not  called  spacial  meridians,  and  the 
point  of  their  crossing  has  not  been  known  as  the  spacial 
pole. 

From  these  two  figures  the  author  has  been  able  to 
construct  Figs.  24  and  25.  He  did  this  by  dividing  both 
Figs.  3  and  4,  along  the  vertical  meridians,  and  then 
pasting  the  divided  parts  together  as  follows:  He  trans- 
posed the  right  half  of  the  left  and  the  left  half  of  the 
right  fields,  and,  bringing  these  together,  he  formed  Fig. 
24,  for  which  there  is  no  name  better  than  binocular 
field  of  vision;  then,  without  transposing,  he  brought  to- 
gether the  left  half  of  the  left  field  and  the  right  half  of 
the  right  field,  thus  creating  Fig.  25,  which  he  has 
named  the  binocular  field  of  vieiv. 

Fig.  24,  although  standing  separate  from,  is,  in  reality, 
a  part  of,  Fig.  25.  Fig.  24  represents  the  field  of  binoc- 
ular vision  when  both  the  head  and  the  eyes  are  station- 
ary and  in  their  primary  positions.  In  this  peculiarly 
shaped  field  every  object  is  seen  by  the  two  eyes;  and 


126  THE    FUNDAMENTAL    PRINCIPLES 

every  object  within  this  field,  further  removed  than  the 
point  of  fixation,  is  seen  singly  by  the  two  eyes,  if 
that  point  is  distant  thirty  or  more  feet.  The  measure- 
ments of  this  field  in  the  four  cardinal  directions  are: 
55°  up,  70°  down,  and  60°  to  the  right  and  left.  In 
the  center  of  this  field  is  the  binocular  spacial  pole,  and 
passing  through  this  pole  are  the  binocular  spacial  me- 
ridians. Encircling  the  pole  are  the  parallels,  located 
10°  apart.  Since  the  field  of  binocular  rotations  is  only 
a  little  smaller  than  the  field  of  binocular  single  vision, 
as  shown  in  Fig.  24,  practically  all  the  points  in  this 
field  may  become  points  of  fixation,  by  rotating  the  eyes, 
while  the  head  remains  stationary.  There  cannot  be  a 
point  in  this  space  which  will  not  lie  on  one  of  the  spa- 
cial meridians,  except  the  point  of  fixation — the  binocular 
spacial  pole — which  lies  on  every  meridian,  at  the  point 
of  their  crossing. 

Two  points  in  space  are  to  be  considered  in  every  ro- 
tation— the  first  point  of  view,  which  is  the  point  of  fixa- 
tion, and  the  second  point  of  view,  which  is  the  point  to  be 
fixed.  The  changing  from  the  one  to  the  other  is  neither 
more  nor  less  than  the  moving  of  the  binocular  spacial 
pole  along  that  binocular  spacial  meridian  on  which  lie 
both  the  first  and  second  points.  If  the  first  point  of 
view  is  the  primary  point,  as  in  Fig.  24,  the  second 
point  may  be  the  point  of  crossing  of  parallel  circle 


OF    OCULAR   ROTATIONS.  127 

40  and  meridian  120-300,  above  (any  other  meridian  and 
parallel  might  have  been  chosen).  In  this  case  the 
point  of  fixation — the  binocular  spacial  pole — would 
move  along"  this  meridian  until  it  reaches  the  point  which 
was  on  circle  40.  In  every  rotation  the  parallel  circles 
move  with  the  pole,  so  that  when  the  pole  (point  of 
fixation)  reaches  the  second  point  of  view,  the  point  of 
crossing  of  parallel  40  and  meridian  120-300,  below, 
will  have  moved  up  to  the  point  which  was  the  primary 
point  before  the  rotation  began.  All  points  that  were 
on  that  meridian  before  the  rotation  began  will  be  on  it 
when  the  rotation  has  ended,  but  they  will  be  differently 
related  to  both  the  binocular  pole  and  the  binocular 
parallels. 

In  the  binocular  field  of  vision  (Fig.  24),  when  the 
head  and  eyes  are  in  their  primary  positions,  every  point 
will  lie  on  three  circles  common,  or  belonging,  to  the  two 
eyes — (1)  a  spacial  meridian  which  determines  the  re- 
lationship (cardinal  or  oblique)  that  the  point  bears  to 
the  vertical  and  horizontal  planes  of  the  head;  (2)  a 
spacial  parallel  which  marks  its  distance  in  degrees  from 
the  line  of  intersection  of  the  two  planes  of  reference;  (3) 
an  isogonal  circle,  primary  or  secondary,  of  some  group, 
which  determines  the  angle  under  which  it  is  seen  by  the 
two  eyes.  Any  one  spacial  meridian  and  any  one  spacial 
parallel  can  cut  each  other  at  only  two  points,  which 


128  THE   FUNDAMENTAL   PRINCIPLES 

points  are  in  opposite  directions  from  the  spacial  pole 
and  equally  distant  from  it. 

The  easy  coexistence  of  the  binocular  spacial  pole,  meri- 
dians, and  parallels  depends  on  normal  conditions  of  the 
ocular  muscles.  There  may  be  a  binocular  spacial  pole 
and  parallels,  but  no  binocular  meridians;  but  such  a 
state  can  be  established  only  by  unconnected  oblique 
astigmatism,  through  abnormal  work  on  the  part  of  the 
obliques.  Normal  recti  and  oblique  muscles  easily  create 
and  maintain  the  binocular  spacial  pole,  meridians  and 
parallels,  as  shown  in  Fig-.  24.  Abnormal  recti  and 
oblique  muscles  make  it  either  difficult  or  impossible  to 
have  the  binocular  spacial  pole,  meridians,  and  parallels. 
The  treatment,  surgical  and  otherwise,  of  abnormal 
muscle  conditions  has  for  its  aim  the  easy  creation  and 
maintenance  of  the  binocular  spacial  pole,  meridians,  and 
parallels. 

Fig.  25  is  a  combination  of  both  the  field  of  binocular 
vision  and  the  field  of  binocular  view.  Objects  located 
anywhere  within  the  white  area  of  Fig.  25  will  be  seen 
with  the  two  eyes — together  if  located  within  the  space 
corresponding  in  shape  and  size  with  Fig.  24,  but  with 
one  or  the  other  eye  only  if  removed  further  from  the 
spacial  pole.  Objects  beyond  parallel  60°  to  the  left 
will  be  seen  with  the  left  eye  only,  and  objects  beyond 


OF    OCULAR    ROTATIONS.  129 

the  same  parallel  to  the  right  will  be  seen  by  the  right 
eye  only. 

The  spacial  pole  of  an  eye  must  be  on  the  same 
straight  line  with  the  anterior  and  posterior  poles  of  the 
eye.  The  spacial  pole  of  an  eye  can  be  the  direct  point 
of  view,  for  that  eye,  only  because  the  center  of  the 
macula  is  the  posterior  pole,  for  the  center  of  the  macula 
and  the  direct  point  of  view  must  be  connected  by  a 
straight  line.  If  the  spacial  pole  for  each  eye  is  the 
direct  point  of  view  for  that  eye,  as  in  Figs.  3  and  4,  the 
fixing  of  the  two  eyes  on  one  point  brings  the  two  poles 
into  one,  as  in  Figs.  24  and  25.  The  perfect  fusion  of 
the  two  poles  brings  into  practical  fusion  the  spacial 
meridians  and  parallels  of  the  two  eyes,  also  well  shown 
in  Figs  24  and  25. 

The  monocular  spacial  parallel  is  everywhere  equally 
distant  from  the  visual  axis  of  the  eye  to  which  it  be- 
longs; therefore,  strictly  speaking,  no  two  circles  equal- 
ly distant  from  the  two  poles  could  be  perfectly  fused, 
for  their  centers  could  not  be  made  the  same  point.  In 
the  formation  of  the  binocular  pole,  the  two  vertical 
spacial  meridians  would  be  perfectly  fused,  but  the  two 
horizontal  spacial  meridians  would  cross  each  other  at 
the  binocular  pole,  and  they  would  then  diverge,  but  so 
slightly  that,  at  90°,  they  would  be  just  that  distance 
apart  corresponding  with  the  measurement  between  the 


130  THE  FUNDAMENTAL,  PRINCIPLES 

two  eyes.  At  the  extreme  limit  of  lateral  binocular  ro- 
tation they  would  be  much  closer  together,  probably  1£ 
inches  or  less.  For  practical  infinity,  so  slight  a  sepa- 
ration would  amount  to  nothing. 

When  the  binocular  spacial  pole  is  at  practical  infinity, 
a  line  going  from  this  pole  to  a  point  halfway  between 
the  two  eyes  may  be  considered  as  the  binocular  vis- 
ual axis.  This  conception  would  give  perfect  binoc- 
ular spacial  meridians  and  parallels.  Fig.  26  has 
been  constructed  on  this  conception,  and  the  mathematics 
of  the  figure  proves  the  value  of  the  conception. 

In  the  study  of  the  Isogonal  Circles  in  Fig.  18,  it  has 
been  stated  that,  for  every  point  on  the  line  of  intersec- 
tion of  the  vertical  and  horizontal  fixed  planes  of  the 
head,  there  is  a  new  group  of  isogonal  circles,  all  the 
members  of  any  one  of  the  infinite  number  of  groups 
having  the  same  diameter.  The  point  of  direct  fixation 
not  only  creates  an  independent  group  of  isogonal  circles, 
but  it  also  creates  an  independent  group  of  binocular 
spacial  meridians  and  an  associated  group  of  binocular 
parallels. 

In  Fig.  26,  the  primary  isogonal  circle  is  constructed 
through  B  and  D,  the  centers  of  the  two  eyes,  and  the 
point  of  fixation,  C.  The  horizontal  binocular  spacial 
meridian,  /-C-/,  for  that  point  of  fixation,  has  been  cre- 
ated by  M-C,  the  binocular  axis,  as  a  radius.  The  ver- 


OF    OCULAR    ROTATIONS. 


131 


132  THE  FUNDAMENTAL   PRINCIPLES 

tical  and  oblique  meridians  of  this  group  would  be  con- 
structed with  the  same  radius.  Binocular  spacial 
meridians,  constituting-  any  one  group,  are  meridians 
with  the  same  radius.  The  binocular  parallels  created 
by  the  point  of  fixation,  C,  are  A'-E' ',  R"-S" ,  V"'-  W" . 

If  G  had  been  chosen  as  the  point  of  fixation,  the  pri- 
mary isogonal  circle  would  have  passed  through  it  and 
the  two  centers  of  rotation,  B  and  D.  With  C'  as  the 
point  of  fixation,  the  binocular  axis,  M-C' ,  as  a  radius, 
would  generate  the  horizontal  binocular  spacial  meridian, 
2-C'-2,  for  that  point,  and  all  the  other  members  of  that 
group  of  spacial  meridians  would  have  the  same  radius. 
The  parallels  for  this  new  group  of  meridians  and  par- 
allels would  be  A-E,  R'-S',  and  V"-W". 

If  C"  had  been  chosen  as  the  point  of  fixation,  then 
the  primary  isogonal  circle  for  that  point  would  have 
passed  through  C"  and  the  two  centers  of  rotation,  B 
and  D.  M-C"  would  have  been  the  binocular  axis  and 
the  radius  of  curvature  for  all  the  binocular  spacial 
meridians  for  that  point.  The  circle  representing  the 
horizontal  binocular  spacial  meridian,  with  M-C"  as 
the  radius,  would  be  j-C"-j.  The  associated  parallels 
would  be  X-S  and  V-  W. 

If  C'"  had  been  chosen  as  the  point  of  fixation,  the 
primary  isogonal  circle  for  that  point  would  have  passed 
through  C"'  and  the  two  centers  of  rotation  B  and  D,  and 


OF    OCULAR    ROTATIONS.  133 

M-C'"  would  have  become  the  binocular  axis.  With  M- 
C'"  as  a  radius,  the  horizontal  binocular  spacial  meridian 
would  be  4-C'"-4,  and  all  the  other  meridians  belonging 
to  the  group  created  by  the  point  C'"  would  have  M-C'" 
as  the  radius.  The  parallel  for  this  group  of  meridians 
and  parallels  would  be  V-  W. 

The  equator  of  any  one  of  these  four  groups  of  meridians 
and  parallels  would  have  the  same  radius  of  curvature  as 
the  meridians.  The  diameter  of  the  equator  of  group  C 
is  X-Z,  that  of  group  C  v&X'-Z' ,  that  of  group  C"  is  X"- 
Z" ,  and  that  of  group  C"  is  X'"-Z'" .  The  diameter  of 
each  equator  is  the  same  as  that  of  the  meridians  be- 
longing to  the  same  group.  The  diameters  of  the  par- 
allels belonging  to  group  C  are  A-E ',  R"-S" ,  and  V'"- 
W";  the  diameters  of  the  parallels  belonging  to  group  C' 
a,reA-J£,  J?'-S',  and  V"-W"\  those  for  group  C"  are  R-  S 
and  V'-W'\  and  the  one  for  group  C"  is  V-W. 

An  interesting  feature  of  Fig.  26  is  that  the  two  in- 
direct visual  lines  drawn  from  A  and  E  respectively,  that 
from  A  through  D,  and  that  from^1  through  B,  intersect 
each  other  on  the  line  M-C.  Lines  similarly  drawn 
from  R  and  ,5*  and  from  Fand  W,  respectively,  would  inter- 
sect each  other  on  the  line  M-C.  Mathematically,  A  and 
E  are  equally  distant  from  C ',  R  and  S  are  equally  dis- 
tant from  C",  and  Fand  PFare  equally  distant  from  C'". 


134  THE   FUNDAMENTAL,    PRINCIPLES 

The  very  definition  of  a  parallel  makes  apparent  the 
correctness  of  the  above  statement. 

A  binocular  spacial  parallel  cuts  the  horizontal  spacial 
meridian  (and  all  other  meridians)  at  only  two  points,  and 
these  points  are  equally  distant  from  the  binocular 
spacial  pole.  This  is  true  of  every  parallel  of  every 
single  group  of  parallels  and  meridians,  as  group  C,  C", 
C",  and  C'".  It  is  through  a  succession  of  such  two 
points  on  diminishing  horizontal  spacial  meridians  that 
the  primary  isogonal  circle  passes,  as  A  and  £,  R  and  S, 
and  Fand  W. 

Three  other  primary  isogonal  circles  could  be  con- 
structed in  Fig.  26,  all  of  which  must  pass  through  the 
centers  of  rotation,  B  and  D.  One  of  these,  in  going 
from  B,  would  pass  through  V ,  R ',  A',  thence  through 
a  new  point  of  fixation  on  M-C  extended,  and  thence  on 
through  £',  6",  and  W  to  D,  thence  to  the  beginning  at 
B.  Another  isogonal  circle  may  start  from  B  and  go 
through  V"  and  R"  on  to  a  still  more  distant  point  of  di- 
rect fixation  on  M-C  extended,  thence  around  to  S", 
through  W"  and  D,  to  the  point  of  beginning  at  B.  And 
again,  a  still  larger  isogonal  circle  may  be  started  at  B, 
carried  thence  through  V"\  to  a  point  of  direct  fixation, 
still  further  removed,  on  the  line  M-C  extended,  around 
to  W"t  thence  through  D  to  B,  the  starting  point. 


OF    OCULAR    ROTATIONS.  135 

Thus  it  is  shown  by  Fig1.  26  that  any  two  points  on 
any  horizontal  binocular  spacial  meridian  cut  by  a 
parallel  circle  may  become  points  of  binocular  single 
vision,  for  these  two  points  either  lie  on  a  constructed  pri- 
mary isogonal  circle  or  in  the  line  of  a  possible  primary 
isogonal  circle. 

There  is  no  point  in  viewable  space  which  is  not  at  the 
crossing  of  a  spacial  meridian  and  a  spacial  parallel  be- 
longing to  some  group;  and  such  points  as  lie  in  the  ro- 
tation field  (only  slightly  smaller  than  that  represented  in 
Pig.  24)  are  also  on  either  the  primary  or  some  secondary 
isogonal  circle  of  some  group — the  three  groups  of  circles 
as  related  to  any  one  point  of  direct  view  constitute  one 
common  triple  group. 

When  the  binocular  spacial  pole  moves  from  point  to 
point  on  the  primary  isogonal  circle — the  first  point  of 
view,  whether  direct  or  indirect,  is  always  on  the  primary 
isogonal  circle — it  moves  along  the  intervening  arc  of 
that  circle,  as  from  C  to  A,  without  change  of  angle  of 
convergence;  or  if  it  moves  along  the  cord  of  that  arc, 
the  angle  of  convergence  increases  as  it  moves  from  C  to 
the  middle  of  the  cord,  and  thence  on  decreases  until 
the  pole  arrives  at  A .  The  angle  at  the  end  of  the  ro- 
tation is  the  same  as  at  the  beginning.  In  this  rotation 
the  pole  has  moved  from  a  point  on  the  horizontal  spacial 
meridian,  /-C-/,  of  one  group,  to  a  point  on  the  horizon- 


136  THE   FUNDAMENTAL   PRINCIPLES 

tal  spacial  meridian,  2-C-2  of  another  group,  but  the 
visual  axes  have  not  left  the  plane  common  to  these  two 
meridians  and  the  retinal  meridian  on  which  were  lying 
the  two  images;  and  the  macula,  in  passing  from  one  image 
to  the  other,  has  not  deviated  from  that  retinal  meridian 
on  which  were  lying  the  two  images  before  the  rotation 
began,  nor  does  it  ever  deviate  from  such  a  meridian. 

If  the  second  point  of  view  is  A',  it  will  be  seen  that 
the  two  points,  C  and  A\  lie  on  the  same  horizontal 
spacial  meridian,  i-C-i.  This  rotation  cannot  be  effected 
without  a  change  of  angle  of  convergence  which  will 
grow  smaller,  for  the  second  point  is  on  a  larger  isogo- 
nal  circle.  The  spacial  pole,  in  moving  from  C  to  A', 
may  go  along  the  arc  C-A'  or  along  the  cord  of  this  arc, 
but  in  either  case  the  angle  of  convergence  has  continually 
changed.  The  maculas  have  moved  from  the  images  of  C 
to  the  images  of  A ',  along  the  horizontal  retinal  meridian. 
Thus  might  be  studied  rotations  from  any  one  point  of 
view  to  any  other  point  of  view,  cardinal  or  oblique. 

Some  one  primary  isogonal  circle  passes  through  the 
two  points  of  intersection  of  all  successively  diminishing 
horizontal  binocular  spacial  meridians  and  any  one  of 
the  parallels  belonging  to  the  same  group. 

Every  secondary  isogonal  circle  cuts  every  parallel  at 
two  points  similarly  related  to  the  spacial  pole  and  the 
vertical  and  horizontal  meridians;  but  at  these  points  it 


OF   OCULAR   ROTATIONS.  137 

cuts  two  different  meridians  which  bear  the  same  relation- 
ship to  the  vertical  and  horizontal  meridians.  This  is 
made  evident  by  the  fact  that  the  spacial  part  of  every 
secondary  isogonal  circle  is  wholly  either  above  or  be- 
low the  plane  of  the  horizontal  spacial  meridian,  while 
one-half  of  every  oblique  meridian,  and  the  vertical  meri- 
dian as  well,  is  above,  and  the  other  half  is  below,  the 
plane  of  the  horizontal  meridian. 

Since  the  two  points  of  intersection  of  a  parallel  and 
any  oblique,  or  the  vertical,  meridian  are  on  opposite 
sides  of  the  plane  of  the  horizontal  meridian,  it  would 
not  be  possible  for  any  secondary  isogonal  circle  to  pass 
through  both  points.  The  primary  isogonal  circle 
passes  through  a  point  common  to  all  meridians  of  any 
one  group,  which  point  is  the  binocular  spacial  pole,  and 
intersects  the  horizontal  meridian  of  all  diminishing 
groups  at  two  points.  The  spacial  part  of  no  secondary 
isogonal  circle  cuts  any  horizontal  spacial  meridian  at 
any  point,  but  every  secondary  circle  cuts  all  other 
meridians,  each  at  only  a  single  point. 

If  the  maculas  were  not  the  posterior  poles  of  the  eyes; 
if  the  centers  of  the  retinal  concaves  were  not  the 
centers  of  rotation;  and  if  all  lines  of  direction  did  not 
cross  each  other  at  the  centers  of  rotation,  then  Fig.  26, 
with  all  of  its  mathematical  beauties,  could  have  no  exist- 
ence; nor  would  Figs.  24  and  25  have  any  true  foundation. 


138 


THE   FUNDAMENTAL   PRINCIPLES 


If  the  macula  is  not  the  posterior  pole,  then  the  mo- 
nocular spacial  pole  cannot  be  on  the  visual  axis,  except 
in  ideal  eyes,  but  would  be  to  its  inner  side  about  5°. 


SO  ffff' 


210 


Fig.  27. 

The  convergence  of  the  two  visual  axes  would  leave  the 
two  spacial  poles  10°  apart,  as  shown  in  Fig-.  27.  A 
binocular  spacial  pole  would  be  impossible,  and  without 


OF   OCULAR    ROTATIONS.  139 

a  binocular  pole  there  could  be  no  binocular  meridians 
and  parallels.  As  shown  in  Fig-.  27,  the  two  vertical 
meridians  would  be  made  parallel  with  each  other,  but 
10°  apart,  while  the  two  horizontal  meridians  seem  to  be 
fused  into  one.  If  such  a  condition  as  depicted  in  Fig-. 
27  were  true,  the  point  of  convergence  of  the  visual  axes, 
in  rotating1,  could  not  move  along1  a  single  meridian  except 
the  horizontal.  The  confusion  in  Fig.  27,  when  con- 
trasted with  the  clearness  of  Fig.  25,  must  conve}r  a 
forceful  lesson  to  the  mind  of  the  searcher  after  the  truth. 

ANGLE  OF  CONVERGENCE. 

In  all  binocular  rotations  the  binocular  spacial  pole  is 
made  to  move  along  the  plane  of  the  binocular  spacial 
meridian  in  which  lie  the  first  and  second  points  of  view. 
The  spacial  meridians  all  accompany  the  motion  of  the 
spacial  pole;  but  that  meridian  whose  plane  is  the  rota- 
tion plane,  and  it  alone,  has  a  wheel-like  motion.  All 
parallels  also  move  with  the  rotating  pole,  but  they  have 
no  wheel-like  motion.  As  the  spacial  pole  rises  or  falls, 
the  planes  of  all  the  parallels  look  up  or  down;  as  the 
pole  moves  to  the  right  or  left,  or  obliquely  up  or  down, 
the  planes  of  the  parallels  face  in  a  corresponding  di- 
rection, but  in  no  case  does  a  parallel  move  in  its  plane. 

Several  interesting  facts  have  already  appeared  in 
connection  with  the  study  of  the  isogonal  circle. 


140  THE   FUNDAMENTAL   PRINCIPLES 

Another  important  feature  growing-  out  of  the  study 
of  the  isogonal  circle  is  the  easy  determination  of  the 
angle  of  convergence,  whatever  may  be  the  distance  of 
the  point  of  fixation.  The  mathematical  formula  for 
solving  this  problem  is  :  As  the  circumference  of  the 
isogonal  circle  is  to  360°,  so  is  the  arc  extending-  from 
the  center  of  one  eye  to  the  center  of  the  other,  divided 
by  2,  to  the  angle  of  convergence. 

The  first  member  of  this  proportion  is  found  by  multi- 
plying the  length  of  the  diameter  of  the  circle,  which  is 
the  distance  of  the  point  of  fixation,  by  3.1416.  The  third 
member  of  the  proportion  depends  on  the  size  of  the  circle 
and  the  distance  between  the  centers  of  the  two  eyes.  If 
the  circle  is  large,  the  arc  from  the  center  of  one  eye  to 
the  center  of  the  other  is  practically  the  same  length  as 
its  chord,  which  is  the  straight  line  from  the  center  of  the 
one  eye  to  the  center  of  the  other.  If  the  diameter  of  the 
circle  is  in  feet,  then  the  arc  must  be  expressed  in  a  frac- 
tion of  a  foot,  but  if  the  one  is  expressed  in  inches,  the 
other  must  be  also.  To  illustrate  :  Let  the  diameter  of 
the  circle  be  16  inches,  and  let  the  arc  subtending  the 
angle  of  the  visual  axes  be  2\  inches,  then  the  following 
is  the  formula  expressed  in  figures  : 

50.26  :360°::2i-2  :  X°. 

From  this  it  will  be  found  that  X=8.9°.  If  the  first  and 
third  members  of  the  proportion  were  feet  and  a  fraction 


OF    OCULAR   ROTATIONS. 


141 


of  a  foot,  and  if  the  arc  subtending  the  angle  formed  by 
the  visual  axes  was  always  2^  inches,  or  i  of  a  foot, 
the  work  of  determining'  the  angle  of  convergence  could 
be  simplified  as  follows  :  Divide  36  (the  result  of  multi- 
plying 360  by  |  -^-  2)  by  the  product  of  the  distance  of 
the  point  of  fixation  (the  diameter  of  the  isogonal  cir- 
cle) and  3.1416.  To  illustrate:  Fixation  is  at  1  foot. 
Multiply  1  by  3. 1416  and  the  product  is  3.1416;  with  this 
number  divide  36  and  the  quotient  will  be  11.35°.  For 
any  given  length  of  the  diameter  of  the  isogonal  circle, 
the  visual  axes  will  form  a  greater  angle  if  the  eyes  are 
wide  apart  than  if  they  are  close  together.  For  compar- 
ison, let  the  diameter  be  16  inches  and  the  arc  2\  inches; 
then  the  angle  of  convergence  will  be,  as  already  shown, 
8.9°;  but  let  the  arc  be  2  inches,  then  the  angle  of  conver- 
gence will  be  7.16°,  a  difference  of  1.74°.  The  following 
table  is  interesting  and  helpful,  and  is  approximately  cor- 
rect. The  point  of  fixation  being  16  inches,  the  upper  row 
of  figures  represents  the  pupillary  distance  and  the  lower 
row  the  angle  of  convergence  of  the  visual  axes  for  each: 


2 

2K 

2% 

2^ 

m 

23/4 

2% 

3 

7.16° 

8.06° 

8.5° 

8.95° 

9.4° 

9.85° 

10.3° 

10.74° 

As  is   well  known,   the   metre-angle  of  Nagel   is  not 
formed  by  the  intersection  of  the  two  visual  axes,  but  it 


142  THE    FUNDAMENTAL    PRINCIPLES 

is  the  angle  formed  by  the  intersection  of  one  visual  axis 
with  the  extended  median  plane  of  the  head,  the  head  in 
the  primary  position,  the  point  of  fixation  being1  at  a  dis- 
tance of  one  meter.  Under  these  conditions,  the  angle 
formed  by  the  visual  axis  of  the  other  eye  and  the  ex- 
tended median  plane  of  the  head,  is  also  a  metre-angle; 
the  one  exactly  equal  to  the  other.  The  sum  of  the  two 
angles  constitutes  the  angle  of  convergence,  so  that  the 
angle  of  convergence  is  two  metre-angles  of  Nagel.  Both 
the  metre-angle  and  the  angle  of  convergence  vary  with 
variations  of  the  distance  between  the  centres  of  the  two 
eyes.  The  angle  of  convergence  is  a  thing  to  be  meas- 
ured, but  not  more  certainly  than  that  the  metre-angle  is 
also  a  thing  to  be  measured.  The  metre-angle,  therefore, 
cannot  be  taken  as  a  standard  of  measurement,  because  a 
standard  must  never  vary.  A  yard  must  be  36  inches, 
whether  one  is  buying  or  selling,  and  whether  the  thing 
bought  or  sold  is  cloth  or  tape.  The  very  word  standard 
means  unvarying.  The  unvarying  standard  for  measur- 
ing angles  is  the  arc  of  a  circle  in  degrees,  minutes,  and 
seconds.  This  standard,  for  reasons  to  be  shown,  should 
apply  to  the  angle  of  convergence.  If  Nagel  had  taught 
that  the  metre-angle  is  the  angle  formed  by  the  intersec- 
tion of  the  visual  axes  at  a  distance  of  one  metre,  and  had 
given  to  it  twice  the  value  in  degrees  that  he  did  give  it, 
there  would  be  less  objection  to  it.  Even  then,  the  me- 


OF    OCULAR    ROTATIONS. 


143 


tre-ang-le  would  mean  3°  20'  with  the  distance  from  center 
to  center  of  the  two  eyes  58mm;  while  it  would  mean 
3°  40'  with  the  distance  from  center  to  center  of  the  two 
eyes  64mm.  After  having-  determined  the  value  of  the 
metre-angle  (the  angle  formed  by  the  intersection  of  the 
visual  axes  of  the  eyes  at  the  distance  of  one  metre,  the 
head  invariably  in  the  primary  position)  in  any  given 
case  it  would  be  very  easy  to  translate  any  fraction  of  a 
metre-angle  or  any  number  of  metre-angles  into  degrees. 
Distances  less  than  a  metre,  therefore  a  fraction  of  a 
metre,  would  increase  the  metre-angle  in  inverse  ratio;  for 
distances  greater  than  a  metre,  the  metre-angle  would 
decrease  in  inverse  ratio.  To  illustrate:  Fixation  at 
i  a  metre  would  give  convergence  of  two  metre-angles; 
g  metre  would  give  a  convergence  of  8  metre-angles;  but 
fixation  at  2  metres  would  give  convergence  of  \  metre- 
angle;  fixation  at  8  metres  would  give  convergence  of  | 
metre -angle.  Let  the  value  of  the  metre -angle  be 
3°  20',  then  the  above  would  be  translated:  2  ma  =  6°  40', 
8  ma  =  26°  40',  \  ma  =  1°  40',  |  ma  ==  25'. 

The  value  of  the  metre-angle  (the  angle  of  convergence) 
for  various  distances  between  the  eyes  is  given  in  the 
accompanying  table  : 


Distance  be- 
tween the  eyes 
in  inches. 

2 

2!/8 

2^ 

2% 

2/2 

2% 

2* 

2-j 

3 

Value  of  one 
metre-angle. 

2°54'38" 

3°5'33" 

3°16"28" 

3°27'23" 

3°38'18" 

3°49'13" 

4°(X8" 

4°11'3" 

4°21'58" 

144  THE    FUNDAMENTAL   PRINCIPLES 

An  interesting1  fact  developed  in  working-  out  the  size 
of  the  metre-angle,  is  that  for  every  g  of  an  inch  in- 
crease of  the  distance  between  the  eyes  there  is  an  in- 
crease of  the  angle  to  the  extent  of  10'  55".  Knowing*  the 
size  of  the  metre-angle  when  the  base-line  (distance  be- 
tween the  centers  of  the  eyes)  is  2  inches,  the  size  of  the 
angle  with  the  base-line  2|  inches  is  found  by  adding  to 
the  former  54'  35",  which  is  5  times  10'  55".  This  would 
give  2°  54'  38"  +  54'  35"=  3° 49'  13",  just  the  size  of  the 
angle  shown  in  the  table,  when  the  base-line  is  2f  inches. 

To  find  the  size  of  the  angle  of  convergence  in  any  given 
case,  when  the  point  of  fixation  is  less  than  one  metre  dis- 
tant, divide  the  size  of  the  metre-angle  in  degrees  by  that 
part  of  a  metre  that  measures  the  distance  of  the  point  of 
fixation,  which,  of  course,  means  that  }~ou  are  to  invert 
the  terms  of  the  divisor  and  multiply.  To  illustrate: 
Fixation  at  16  inches  is  fixation  at  (14-,  metre.  Let  the 

i.4b 

base-line  be  2i  inches  and  we  have  the  following : 
3°  38'  18"  -H  tt  --=  3°  38'  18"  X  ™  =  8°  57'  1". 

Again,  let  the  point  of  fixation  be  3  m,  and  the  base-line 
be  2J  inches.  We  now  have 

3°  38'  18"  -^-3  =  3°  38'  18''  X  |  =  1°  12'  46", 

the  size  of  the  angle  of  convergence  at  3  m.  The  base- 
line remaining  the  same,  the  angle  of  convergence  at  a 
distance  less  or  greater  than  one  metre,  is  to  the  angle  of 


OF    OCULAR   ROTATIONS.  145 

convergence  at  one  metre  (the  metre-angle),  inversely, 
as  the  distance  of  the  point  of  fixation  is  to  one  metre. 
The  mathematical  formula  is  that  the  tangent  of  half 
the  angle  of  convergence  varies  inversely  as  the  dis- 
tance of  the  point  of  fixation  from  the  middle  of  the  line 
joining  the  centers  of  the  eyes.  But  for  small  angles 
the  above  rule  gives  approximately  the  same  results. 

The  reason  for  suggesting  that  the  metre-angle  be  the 
angle  formed  by  the  intersection  of  the  visual  axes  at  one 
metre,  and  not  the  angle  formed  by  the  visual  axis  and 
the  extended  median  plane,  and  that  it  be  given  a  value 
double  that  given  it  by  Nagel,  is  that  the  angle  of  con- 
vergence, or  rather  the  nervous  impulse  from  the  third 
conjugate  center,  necessary  to  make  this  angle,  is  the 
chief  factor  in  the  formation  of  judgment  as  to  distance. 
In  fixing  points  to  the  right  and  left  on  the  isogonal  curve 
the  angle  formed  by  the  intersection  of  the  visual  axis 
and  the  median  plane  of  the  head  is  confined  to  one  eye, 
and  is  constantly  changing  in  value,  whereas  the  metre- 
angle,  which  is  synonymous  with  the  angle  of  convergence 
of  the  visual  axes  at  one  metre,  remains  the  same  every- 
where when  carried  along  the  isogonal  curve. 


CHAPTER  II. 


ORTHOPHORIA. 


THE  terminology  introduced  by  Stevens  for  indicating 
the  relationship,  normal  and  abnormal,  between  the  oc- 
ular muscles,  being1  of  pure  derivation,  leaves  no  room 
for  change  and  but  little  room  for  addition.  These  terms 
are  so  widely  used  and  are  now  so  well  known,  they  need 
mentioning1  only  when  used  in  connection  with  the  condi- 
tions indicated  by  them.  The  Stevens  nomenclature  was 
adopted  as  both  scientific  and  correct,  by  the  section  of 
Ophthalmology  of  the  American  Medical  Association,  at 
the  Washington  meeting  in  1891. 

Orthophoria  is  the  term  applied  to  a  perfect  balance 
of  the  ocular  muscles  when  the  head  is  in  the  primary 
position  and  the  eyes  are  looking  straight  forward.  This 
condition,  in  the  strictest  sense,  includes  the  idea  that 
the  twelve  extrinsic  muscles  have  all  been  perfectly  devel- 
oped, that  each  has  its  correct  origin,  pursues  its  proper 
course  through  the  orbit  to  the  eye,  and  is  rightly  at- 
tached to  the  globe;  and  that  the  orbits  themselves  are 
perfectly  formed.  It  also  includes  the  idea  that  the  nine 
conjugate  innervations  are  wanting  in  nothing.  When 

(146) 


ORTHOPHORIA.  147 

such  a  state  of  thing's  exists,  the  visual  axes  are  easily 
kept  in  the  same  plane  through  the  first  and  second  con- 
jugate innervations;  are  always  perfectly  converged 
through  the  third  conjugate  innervation;  and  by  means 
of  the  first,  second,  fourth,  and  fifth  conjugate  innerva- 
tions, are  made  to  sweep  harmoniously  along  the  hori- 
zontal plane,  in  the  vertical  plane,  and  in  any  oblique  di- 
rection. Nor  will  the  sixth,  seventh,  eighth,  and  ninth 
conjugate  innervations  fail  to  keep  the  vertical  axes  of 
the  eyes  parallel  with  each  other  and  with  the  median 
plane  of  the  head,  while  the  transverse  axes  lie  in  the 
plane  of  the  primary  isogonal  circle,  regardless  of  the  lo- 
cation of  the  point  of  fixation.  Such  a  condition  would 
also  include  the  idea  that  the  verting  and  ducting  power  of 
all  of  these  muscles  is  up  to  the  standard.  But  for 
these  eyes,  thus  well  balanced,  to  be  perfect,  there  must 
be  no  error  of  refraction.  There  are  such  eyes,  and  the 
happy  possessor  of  them  knows  of  their  existence  only 
for  the  joy  they  give  him.  The  workings  of  such  eyes 
never  add  anything  to  the  sum  of  human  ills. 

There  are  accurate  instruments  for  determining  the  ex- 
istence of  orthophoria.  The  Stevens  phorometer,  the  only 
one  in  use  for  a  few  years,  is  represented  in  Figs.  28  and  29. 
This  instrument  being  incapable  of  making  all  the  tests, 
even  for  orthophoria,  it  was  natural  that  others  should 
be  invented,  and  that  the  evolution  would  go  on  to  final 


148  ORTHOPHORIA. 

perfection.  The  Stevens  instrument  is  capable  only  of 
showing-  the  state  of  balance  between  the  different  pairs 
of  muscles,  and  in  that  much  can  determine  the  existence 
of  orthophoria  but  not  the  kind,  for,  after  all  that  has 
been  said,  there  are  two  kinds  of  orthophoria.  It  cannot 
acquaint  the  operator  with  the  duction  power  of  a  sin- 
gle muscle.  It  cannot,  nor  can  any  other  phorometer, 
already  known  or  hereafter  to  be  invented,  give  informa- 
tion about  the  verting  power.  One  serious  objection  to 
the  Stevens  phorometer,  which  applies  with  equal  force 
to  the  Wilson  phorometer  next  to  be  considered,  is  that  it 
is  a  binocular  instrument,  and  to  that  extent  must  be 
faulty.  In  all  phorometers,  either  diplopia  must  be  pro- 
duced by  prismatic  action,  the  images  in  the  two  eyes 
being  on  non-corresponding  points  of  the  retinas,  or  the 
image  in  one  eye  must  be  made  very  different  from  the 
image  in  the  other,  as  by  the  Maddox  rod,  so  as  to  de- 
prive the  guiding  sensation  of  the  reins  of  control.  In 
the  Stevens  phorometer  both  images  are  displaced  so  that 
neither  eye  can  be  in  the  primary  position  while  under 
test.  Again,  if  the  patient  be  not  orthophoric,  rotation 
of  the  instrument  to  properly  relate  the  two  images, 
moves  the  image  in  each  eye,  which  must  be  a  source  of 
inaccuracy. 

The  method  of  using  the  Stevens  phorometer  is  simple. 
A  candle  or  gas  jet  is  placed  twenty  feet  from  the  pa- 


ORTHOPHORIA. 

tient,  who,  in  the  sitting-  posture,  should  hold  his  head 
erect.  Placing-  the  instrument  before  him,  he  looks  at 
the  Jig-fat  throug-h  the  prisms,  when  diplopia  must  become 


Fig.  28. 

manifest.  In  testing-  for  lateral  orthophoria  the  lights 
are  made  to  appear  the  one  above  the  other,  by  rotating 
the  instrument  so  that  the  base  of  one  prism  may  be  di- 


150  ORTHOPHORIA. 

rectly  up  and  the  base  of  the  other  down.  In  orthopho- 
ria  a  vertical  imaginary  line  will  connect  the  two  lights. 
If  the  one  is  not  directly  above  the  other,  there  is  not 
lateral  orthophoria.  The  slightest  movement  of  these 
prisms  will  change  the  relationship  of  the  images,  and  in 
this  way  whatever  error  may  exist  is  measured. 


Fig.  29. 

In  the  test  for  vertical  orthophoria,  the  instrument  is 
so  rotated  as  to  place  the  prisms  with  bases  directly  in. 
The  two  lights  should  now  be  the  same  height,  but  if 
not,  then  there  is  not  vertical  orthophoria.  The  rota- 
tion necessary  to  make  the  lights  level  shows  the  kind 
and  quantity  of  the  error. 

This  instrument  can  also  determine  the  existence  of 
oblique  orthophoria.  It  must  be  rotated  into  the  posi- 


ORTHOPHORIA. 


151 


tion  for  testing  for  lateral  orthophoria;  but,  for  the 
light,  a  horizontal  line  must  be  substituted.  The  line 
will  be  doubled  by  the  prisms  and  they  should  be  par- 
allel with  each  other. 

The   test  of  the  lateral  muscles  and  of  the  obliques 
should  be  resorted  to  in  the  near  also.      For  the   former, 


Fig.  30- 

a  card  with  a  dot  or  cross  in  its  center  must  be  held  at 
the  reading1  distance;  for  the  latter,  a  card  with  a  hori- 
zontal line  on  it  should  be  held  in  the  same  manner.  The 
dots  and  the  lines  should  bear  the  same  relationship  as  in 
the  distant  test.  These  tests  made,  the  Stevens  phorom- 
eter  can  do  no  more. 


152  ORTHOPHORIA. 

The  Wilson  phorometer,  Fig-.  30,  can  do  all  that  the 
Stevens  phorometer  is  capable  of  doing;  and,  besides,  can 
determine  the  duction  power  of  all  the  recti.  The  diplo- 
pia  with  this  instrument  is  produced  by  a  prism  of  10° 
(found  in  one  of  the  opening's  in  the  revolving1  disc)  be- 
fore the  right  eye,  whose  base  can  be  placed  up  for  a  test 
of  the  lateral  muscles,  or  in,  for  a  test  of  the  vertically- 
acting-  muscles.  In  lateral  orthophoria  the  two  images 
will  be  in  a  vertical  line,  when  the  slightest  turning  of 
the  rotary  prism  constituting  that  part  of  the  instrument 
which  is  always  before  the  left  eye,  will  displace  the  up- 
per (true)  image  either  to  the  right  or  left.  Should  the 
lower  image  not  be  in  a  vertical  line  with  the  upper,  mov- 
ing the  rotary  prism  until  the  one  is  directly  above  the 
other  will  show  both  the  kind  and  the  quantity  of  the 
error.  Changing  the  position  of  the  disc,  the  10°  prism 
will  present  its  base  towards  the  nose.  When  the  im- 
ages are  found  in  the  same  horizontal  plane  there  is  ver- 
tical orthophoria,  and  the  slightest  movement  of  the  ro- 
tary prism  will  elevate  or  depress  the  one  seen  by  the  left 
eye.  Should  the  false  image  be  higher  or  lower  than  the 
true,  moving  the  rotary  prism  in  the  proper  direction 
will  bring  the  true  image  into  the  horizontal  plane  with 
the  false,  thus  showing  both  the  kind  and  quantity  of  the 
vertical  error.  Thus  far  the  workings  of  these  two  in- 
struments practically  correspond,  the  one  being  no  bet- 


ORTHOPHORIA.  153 

ter  than  the  other.  With  the  Stevens  instrument  both 
images  are  moved  in  every  rotation;  with  the  Wilson  in- 
strument only  the  true  image  is  made  to  change  position. 
In  connection  with  each  of  these  phorometers  there  is  the 
indispensable  spirit  level. 

With  the  open  space  of  the  disc  before  the  right  eye 
and  the  rotary  prism  in  a  neutral  state  before  the  left 
eye,  the  prism  axes  being  horizontal,  by  moving  the  ro- 
tary prism,  the  duction  power  of  the  superior  and  infe- 
rior recti  can  be  taken,  which  should  be  3° — certainly  not 
less  than  2° — for  each.  Since  this  revolving  prism  can 
measure  10°,  it  can  always  show,  practically,  the  duction 
power  of  the  vertically-acting  muscles.  Turning  the  ro- 
tary prism  again  into  a  neutral  state,  so  the  axis  may  be 
vertical,  still  keeping  the  open  space  before  the  other  eye, 
abduction  can  be  taken,  which,  in  orthophoria,  should 
be  8° — certainly  not  less  than  6°.  Rotating  it  in  the  other 
direction,  adduction  can  be  taken  only  up  to  10°,  its  max- 
imum power.  To  go  higher  than  this,  the  disc  before 
the  right  eye  must  be  revolved  until  the  15°  prism  is 
brought  into  position,  base  out.  Now,  starting  the  ro- 
tary prism  in  the  adduction  arc,  every  movement  adds  to 
the  15°  adduction  caused  by  the  prism  before  the  right 
eye,  until,  when  the  end  of  the  arc  has  been  reached,  25° 
of  adduction  is  shown.  The  doubling  just  now  occur- 
ring, the  conclusion  is  that  adduction  is  normal;  if  soon- 


154  ORTHOPHORIA. 

er,  that  it  is  below  normal.  It  cannot  be  carried  higher 
by  this  instrument.  It  will  be  noticed  that  the  test  has 
been  applied  not  to  one  internus,  but  to  both,  and  for 
this  reason  cannot  be  reliable. 

The  Wilson  phorometer  is  also  capable  of  testing-  the 
balance  and  imbalance  of  the  oblique  muscles.  To  do 
this,  the  open  space  in  the  disc  is  placed  before  the  right 
eye,  while  the  rotary  prism  is  before  the  left  in  the  neu- 
tral position,  axis  horizontal.  By  revolving-  the  prism  as 
if  testing  for  superduction,  the  point  is  finally  reached 
when  the  horizontal  line,  which  is  now  the  test  object, 
becomes  double.  If  these  two  lines  are  parallel,  then 
for  that  direction  at  least,  there  is  orthophoria  of  the 
obliques.  Returning  to  the  neutral  position,  the  prism 
should  next  be  revolved  in  the  direction  of  sub-duction. 
Presently  the  line  is  again  doubled,  the  false  line  being 
below  the  true.  If  these  lines  are  parallel,  again  there 
is  evidence  of  orthophoria  of  the  obliques.  Not  infre- 
quently the  false  line  in  the  latter  position  will  show  an 
insufficiency  of  the  superior  obliques,  while  in  the  former 
position  the  lines  may  be  parallel.  By  slowly  revolving 
the  prism  back  towards  the  neutral  point,  whether  from 
the  one  direction  or  the  other,  the  patient  can  observe 
whether  or  not  the  fusion  of  the  two  lines  is  simultane- 
ous throughout,  or  whether  the  fusion  takes  place  at  one 
end  and  then  gradually  throughout.  When  the  lines  are 


ORTHOPHORIA. 


not  parallel,  the  kind  of  dipping-  indicates  the  character 
of  error.  This  instrument  is  wholly  incapable  of  testing- 
the  lifting-  power  of  the  obliques. 


Neither  one  of  these  instruments  is  constructed  on  the 
correct  principle  underlying  the  tests  of  the  ocular  mus- 
cles, even  when  orthophoria  exists.  The  principle  on 
which  all  the  tests  possible  to  a  phorometer  rest,  is  that 
the  imag-e  in  one  eye,  throug-hout  every  test,  shall  be  un- 


156  ORTHOPHORIA. 

disturbed;  that  the  head  shall  be  erect;  and  that  both 
eyes  and  the  object — better  a  white  dot  on  a  black  back- 
ground— shall  be  on  the  extended  horizontal  plane  of  the 
head.  The  false  object  must  have  its  image  thrown  out- 
side the  area  of  binocular  fusion  in  the  eye  under  test, 
while  the  true  object  will  have  its  image  on  the  macula 
of  the  eye  not  under  test,  thus  making  it  not  only  possi- 
ble, but  necessary,  that  this  eye  shall  be  in  the  primary 
position  throughout  the  test,  for  it  is  not  to  have  its  im- 
age disturbed  during  any  one  of  the  several  tests.  An 
instrument  based  on  the  principle  enunciated  above  is 
the  monocular  phorometer.  It  fulfills  every  essential 
condition,  and  is  wholly  reliable,  and,  except  in  rare 
cases,  is  invariable.  The  accompanying  cut,  Fig.  31, 
represents  its  appearance,  but  not  its  capabilities.  The 
screw-and-spring  arrangement,  for  regulating  the  spirit 
level,  is  as  good  as  the  best.  In  the  base  of  the  instru- 
ment there  are  slots  on  either  side  of  the  rotary  prism, 
in  one  of  which,  towards  the  patient's  face,  is  to  be 
placed  the  displacing  prism  for  causing  the  diplopia.  If 
the  instrument  has  been  leveled,  this  prism,  when  placed 
in  the  slot,  must  have  its  axis  either  vertical  or  horizon- 
tal, and  must  produce  a  corresponding  diplopia.  The 
rotary  prism  differs  from  the  one  in  the  Wilson  phorom- 
eter in  that  it  has  a  face  correctl}'  lettered  and  marked 
in  degrees,  for  each  eye,  and  is  easily  reversible. 


ORTHOPHORIA.  157 

With  the  instrument  properly  leveled  before  the  right 
eye,  the  axis  of  the  rotary  prism  vertical,  and  the  6°  prism 
base  up,  in  the  slot  toward  the  face,  the  false  object  is 
made  to  appear  below  the  true,  and  if  directly  under  it, 
there  is  lateral  orthophoria.  The  rotary  prism  turned 
in  either  direction  will  make  the  false  object  go  either  to 
the  right  or  to  the  left  of  the  vertical  line  through  the 
true  object,  which  must  be,  at  all  times,  the  one  looked 
at.  Should  the  false  object  not  be  under  the  true,  turn- 
ing the  rotary  prism  in  the  proper  direction  will  place 
it  there.  On  the  face  of  the  instrument  toward  the  op- 
erator, can  be  read  the  kind  and  quantity  of  the  error. 
The  test  for  lateral  orthophoria,  in  the  near,  is  made 
by  holding  a  card  with  a  dot  or  cross  in  its  center,  at  the 
reading  distance.  To  test  the  vertically-acting  muscles, 
the  rotary  prism  must  be  turned  so  as  to  have  the  revolv- 
ing screw  vertical,  and  the  axis  horizontal.  The  10° 
displacing  prism,  base  in,  must  be  placed  in  the  slot  to- 
wards the  patient's  face,  so  as  to  displace  the  image 
beyond  the  area  of  binocular  fusion.  The  false  object 
should  be  in  the  same  horizontal  plane  with  the  true, 
if  there  is  vertical  orthophoria.  Any  movement  of  the 
rotary  prism  will  displace  the  false  object,  either  rais- 
ing or  depressing  it.  When  the  false  object  is  not 
found  on  a  level  with  the  true,  there  is  a  vertical  hetero- 
phoria.  Turning  the  rotary  prism  so  as  to  bring  the 


158  ORTHOPHORIA. 

false  object  to  a  level  with  the  true,  shows,  on  the  face 
towards  the  operator,  the  kind  and  quantity  of  the  ver- 
tical error. 

With  the  instrument  in  the  adjustment  for  detecting- 
vertical  orthophoria,  and  without  a  displacing1  prism,  the 
balance  of  the  obliques  is  found  by  moving-  the  rotary 
prism,  first  down,  while  the  patient  looks  at  a  hori- 
zontal line  until  it  doubles.  The  lines  will  be  parallel 
if  there  is  orthophoria  of  the  obliques.  Reversing-  the 
movement  of  the  rotary  prism,  the  false  line  appears 
above  the  true,  but  should  be  parallel  with  it.  If  there 
is  not  a  perfect  balance  between  the  obliques  it  will 
be  shown  by  a  want  of  parallelism  between  the  false 
and  true  lines.  The  kind  of  error  will  be  indicated  by 
the  direction  in  which  the  lines  converge,  but  the  quan- 
tity cannot  be  measured  by  this  instrument. 

With  the  instrument  still  in  the  adjustment  for  the 
vertical  muscles,  sub-duction  and  superduction  may  be 
quickly  determined,  as  by  the  Wilson  phorometer.  Ad- 
justing1 it  as  for  testing-  the  lateral  muscles,  abduction 
can  be  taken  without  the  aid  of  a  supernumerary  prism, 
if  the  patient  is  orthophoric.  To  take  the  adduction, 
one  or  two  supernumerary  prisms  will  have  to  be  used 
to  aid  the  rotary  prism.  If  adduction  is  not  above  25°, 
the  15°  prism  may  be  placed  in  the  slot  toward  the 
face,  with  its  base  toward  the  temple.  Turning-  the  ro- 


ORTHOPHORIA.  159 

tary  prism  will  add  to  the  effect  of  the  supernumerary 
prism  up  to  10°.  This  added  to  15°  gives  25°  of  adduc- 
tion, provided  the  doubling-  occurs  only  at  the  end  of  the 
rotation.  If  the  adduction  should  be  30°,  or  more,  it  can 
be  shown  by  placing-  the  5°  or  10°  prism,  base  out,  in  the 
slot  in  front,  while  the  15°  prism  remains  behind,  and 
again  moving-  the  rotary  prism  throug-h  the  nasal  quad- 
rant. This  instrument  can  measure  adduction  only  up 
to  35°.  In  testing-  for  the  adduction  with  the  monocular 
phorometer,  the  only  muscle  to  respond  is  the  one  inter- 
nal rectus. 

By  reversing  the  instrument  all  of  these  tests  can  be 
repeated  on  the  muscles  of  the  left  eye.  In  every  one 
of  these  tests  the  imag-e  in  one  eye  remains  undisturbed. 
The  object  seen  by  this  eye  must  always  be  seen  by  di- 
rect vision,  while  the  false  object  must  be  seen  by  indi- 
rect vision. 

The  simpler  methods  of  testing-  for  orthophoria  of 
the  recti,  even  including-  the  use  of  the  Maddox  rod,  are 
"all  faulty  and  should  be  discarded.  The  leveling-  part 
of  a  phorometer  is  an  absolute  necessity,  for  without 
it  there  can  be  no  exactness  in  the  placing-  of  prisms  be- 
fore an  eye.  In  testing-  for  lateral  orthophoria,  slight 
errors,  resulting  from  an  improperly-placed  prism,  could 
be  tolerated,  but  not  so  in  testing  for  vertical  orthopho- 
ria. The  Maddox  rod  is  objectionable  in  all  tests  of  the 


160  ORTHOPHORIA. 

recti  for  the  reason  that  a  part  of  the  streak  of  light, 
whether  it  be  vertical  or  horizontal,  will  fall  on  the 
field  of  binocular  fusion,  unless  the  error  be  great.  The 
false  image,  whatever  may  be  its  character,  should  nev- 
er be  on  any  part  of  this  field;  otherwise  a  greater  or 
less  effort  at  fusion  will  be  made. 

There  is  a  legitimate  use  for  the  Maddox  rod.  It  is 
in  testing  the  oblique  muscles,  both  as  to  their  ortho- 
phoria  and  their  intrinsic  strength.  This  instrument 
may  be  called  the  cyclo-phorometer,  though  Stevens 
has  named  the  instrument  he  has  invented  for  this  pur- 
pose the  clinoscope.  The  first  of  these  instruments 
was  invented  by  Price,  in  1893,  and  was  exhibited  by 
him  before  the  Section  of  Ophthalmology,  at  the  meet- 
ing of  the  American  Medical  Association  in  San  Fran- 
cisco, in  1894.  It  consisted  of  a  double  prism,  line  of 
bases  horizontal  and  a  rod  at  right-angles  to  this  line  of 
union,  placed  in  a  circular  disc  to  fit  the  rim  of  a  trial 
frame,  and  a  Maddox  rod  only  to  be  placed  vertically  in 
the  other  side  of  the  frame.  Looking  at  a  candle,  the 
patient  would  see  two  horizontal  and  necessarily  parallel 
lines  of  light  with  the  one  eye,  and  a  single  horizontal 
line  of  light  with  the  other,  the  latter  appearing  be- 
tween the  other  two,  and  parallel  with  them  in  ortho- 
phoria  of  the  obliques.  This  was  for  testing  the  ob- 
liques when  the  visual  axes  were  approximately  paral- 


ORTHOPHORIA.  161 

lei.  It  was  faulty  in  that  there  was  no  adjustment  by 
means  of  which  the  frames  holding-  the  rods  could  be 
leveled.  A  little  later,  Baxter,  of  Boston,  and  Brewer, 
of  Connecticut,  each  independently,  invented  a  cyclo- 
phorometer,  with  the  error  in  the  Price  instrument  elim- 
inated. Brewer,  not  knowing  of  the  Price  invention 
when  he  made  claim  for  himself,  later  wrote  to  the 
Ophthalmic  Record  as  follows:  "Dr.  G.  H.  Price,  of 
Nashville,  Tenn.,  appears  in  your  July  [1898]  issue  as 
claimant  to  prior  use  of  the  Maddox  rods  in  testing  the 
position  of  the  retinal  meridians.  Since  he  very  clearly 
substantiates  his  claim,  so  far  as  I  am  concerned  I  tend 
him  such  laurels  as  I  may  have  grasped,  and  trust  he 
may  wear  them  securely  and  gloriously."  Dr.  Brewer 
named  his  instrument  the  torsiometer.  Later  than  this 
Stevens  brought  out  his  prism  clinoscope,  the  construc- 
tion of  which  is  not  very  different  from  the  instruments 
of  Baxter  and  Brewer. 

The  cyclo-phorometer  must,  of  necessity,  be  a  binocu- 
lar instrument.  The  cyclo-phorometer,  Fig. 32, made  for 
use  in  connection  with  the  monocular-phorometer  stand, 
or  the  Wilson  phorometer  holder,  consists  of  a  base  on 
which  rest  two  graduated  cells  (E),  in  each  of  which  is 
to  be  placed  a  triple  Maddox  rod  (H)  with  the  axis  verti- 
cal. Behind  each  of  these  circular  cells  is  a  rectangular 
cell  (F)  for  a  displacing  prism.  There  is  an  arrange- 


162 


ORTHOPHORIA. 


ment  (D)  by  means  of  which  the  pupillary  distance  can  be 
easily  regulated  so  that  the  one  streak  of  light  may  be 
brought  directly  under  the  other.  There  is  beneath  the 
base  of  the  instrument,  a  spirit  level  (L)  for  regulating 


A  - 


Fig.  32- 

the  adjustment  of  the  instrument.  On  each  disc  contain- 
ing the  rods  is  marked  below  a  line  continuous  with  the 
axis  of  the  central  rod.  The  rods  placed  vertically,  with 
a  prism  of  5°  base  up  behind  one  of  them,  will  show  two 


ORTHOPHORIA.  163 

horizontal  lines  of  light,  when  a  candle  is  looked  at.  The 
lower  one  will  be  seen  by  the  eye  before  which  is  the 
combination  rod-and-prism.  The  lines  should  be  paral- 
lel, and  their  ends  even.  The  latter  can  be  regulated 
by  turning-  the  screw  (D)  that  controls  the  pupillary  dis- 
tance. The  slightest  movement  of  either  disc  will  cause 
a  loss  of  parallelism  of  the  streaks  of  light.  If  not  par- 
allel, there  is  want  of  orthophoria  of  the  obliques,  the 
kind  and  quantity  of  the  error  being  shown  b}r  the  rota- 
tion of  either  disc. 

By  removing  the  displacing  prism,  the  intrinsic  power 
— the  cyclo-duction — of  each  oblique  muscle  can  be  taken 
alone,  and  then  the  combined  cyclo-duction  of  either  both 
superior  or  both  inferior  obliques.  This  is  done,  when 
only  one  muscle  is  being  tested,  by  revolving  the  one  rod 
in  the  temporal  arc  for  a  superior,  and  in  the  nasal  arc 
for  an  inferior  oblique.  If  both  superior  obliques  are 
under  the  duction  test,  then  both  rods  must  be  revolved 
in  the  temporal  arc;  if  both  inferior  obliques,  then  both 
rods  must  be  revolved  in  the  nasal  arc.  The  moment  the 
two  streaks  separate,  the  rotations  must  stop.  On  the 
arc  of  the  cell  the  extent  of  cyclo-duction  can  be  read. 
The  normal  cyclo-duction  for  a  single  oblique  muscle  is 
somewhere  between  7°  and  14°.  The  combined  cyclo- 
duction  of  either  pair  of  obliques  is  somewhere  between 
12°  and  22°. 


164 


ORTHOPHORIA. 


The  method  of  determining  the  perfect  balance  of  the 
oblique  muscles,  or  the  imbalance  when  it  exists,  by  the 
Stevens  clinoscope,  will  be  better  understood  after  a  de- 
scription of  the  instrument  itself.  This  description  is 
given  in  the  words  of  the  inventor: 


Fig-  33- 

"The  clinoscope  [Fig.  33]  is  composed  essentiall}"  of 
two  hollow  tubes,  each  of  which  has  at  one  end  a  minute 
pin-hole  opening  through  which  the  eye  can  look,  and  at 
the  other  end  a  translucent  disc  on  which  is  drawn  a  line, 
in  the  case  of  one  tube  from  the  centre  straight  up,  and 
in  that  of  the  other  tube  straight  down. 

"  These  tubes  are  so  adjusted  on  a  standard  that  they 
can  be  placed  and  maintained  in  the  same  horizontal 
plane,  which  is  indicated  by  a  spirit  level,  but  from  end 
to  end  the}7  can  be  directed  horizontally  or  up  or  down. 


ORTHOPHORIA.  165 

They  can,  as  above  intimated,  be  made  to  converge  or 
diverge  to  meet  certain  contingencies. 

"The  tubes  rotate  on  their  long  axes,  and  a  pointer 
attached  to  each  tube  indicates  on  a  scale  the  extent  to 
which  the  tube  is  rotated.  The  small  sight  openings  are 
so  adjustable  that  the  distance  between  them  may  be 
suited  to  the  interpupillary  distance  of  different  persons. 
For  the  accommodation  of  those  who,  on  account  of  pres- 
byopia, myopia,  or  any  high  degree  of  refractive  error, 
cannot  see  at  the  distance  of  the  test  objects  from  the 
eyes,  there  are  clips  in  which  refracting  glasses  ma}"  be 
placed.  The  sight  openings  being  very  small  and  ex- 
actly in  the  same  horizontal  plane,  there  can  be  no  doubt 
as  to  the  erect  position  of  the  median  plane  of  the  head 
when  the  two  eyes  are  seeing,  each  through  its  appropri- 
ate sight  opening,  any  existing  hyperphoria  being  cor- 
rected. 

"The  instrument  is  to  be  so  adjusted  in  respect  to 
height  that  the  sight-holes  will  be  on  a  level  with  the 
eyes  of  the  examined  person  when  sitting  erect.  This 
is  best  accomplished  by  the  use  of  an  adjustable  table. 
The  tubes  may  be  exactly  parallel  or  they  may,  in 
certain  cases,  be  made  to  converge  very  slightly,  thus 
making  the  distant  point  at  8  or  10  feet  instead  of 
infinite  distance.  Under  other  exceptional  circum- 
stances they  may  be  made  to  diverge.  The  tubes 


166  ORTHOPHORIA. 

must  be  brought  to  an  exact  level  with  each  other 
as  shown  by  the  spirit  level. 

"Unless  the  subject  of  the  examination  is  unable  to 
see  the  test  lines  of  the  tubes,  on  account  of  presbyopia 
or  high  refractive  error,  no  glasses  should  be  used,  and 
when  glasses  are  necessary  the  weakest  that  will  enable 
the  person  to  see  the  lines  clearly  should  be  placed  in  the 
clips.  A  prism  for  the  correction  of  hyperphoria  may 
also  be  required.  The  glasses  should  not  be  worn,  since, 
if  a  strong  glass  should  not  be  held  exactly  at  right- 
angles  with  the  axis  of  the  tube,  the  lens  would  itself 
induce  a  declination  of  the  image. 

"  The  examiner  must  be  sure  that  the  examined  person 
sees  through  both  openings  simultaneously,  and  that  the 
view  of  both  images  is  maintained  throughout  the  exam- 
ination; otherwise  there  can  be  no  certainty  that  the 
head  is  precisely  erect. 

"When  the  examined  person  has  secured  a  good  view 
of  both  the  test  lines,  he  should  endeavor,  if  they  do  not 
at  once  unite,  to  induce  them  to  do  so  as  in  a  stereoscope. 
Some  people  do  not  succeed  in  this,  in  which  cases  the 
examination  may  go  on  with  the  images  separated,  but  it 
is  less  satisfactory. 

"When  the  apparent  vertical  position  of  the  lines  has 
been  attained,  the  examiner  should  move  them  more  or 
less  backward  and  forward,  in  order  that  the  true  posi- 


ORTHOPHORIA.  167 

tion  may  be  more  positively  located.  Few  people  can 
arrive  at  a  satisfactory  conclusion  regarding-  the  position 
of  the  lines  at  the  first  trial,  but  after  a  da}7  or  two  the 
tests  become,  for  nearly  all  intelligent  people,  remark- 
ably uniform." 

With  the  clinoscope  thus  adjusted,  the  head  of  the  pin 
with  the  point  up  should  be  fused  with  the  head  of  the 
pin  whose  point  is  down,  and  both  pins  should  be  verti- 
cal if  the  oblique  muscles  are  doing1  their  full  duty — if 
the  vertical  axes  of  the  eyes  are  parallel  with  the  median 
plane  of  the  head.  If  the  two  pins  are  not  now  one  ver- 
tical line  there  is  a  cyclophoria.  Whether  the  C}TC!O- 
phoria  is  plus  or  minus  is  easily  determined,  and  its 
quantity  is  measured  by  revolving  the  tubes  till  the  two 
pins  become  one  vertical  line. 

In  determining  cyclo-duction  by  the  clinoscope,  the 
translucent  discs  with  lines  entirely  across  are  to  be 
used  instead  of  those  that  have  the  lines  only  half  way 
across.  With  the  tubes  properly  adjusted  the  two  lines 
would  be  seen  as  one.  Revolving  one  tube  would  tend  to 
displace  the  image  of  one  line,  which  the  eye  would  over- 
come by  torsioning,  as  long  as  possible.  The  conclusion 
which  Stevens  has  reached  is  that  the  image  may  be  dis- 
placed as  much  as  14°  in  one  eye  before  doubling  occurs, 
and  that  the  combined  displacement,  in  opposite  direc- 
tions, of  the  images  in  the  two  eyes,  may  be  as  much  as 


168  ORTHOPHORIA. 

22°.  He  also  claims  that  a  little  greater  displacement 
may  be  overcome  by  the  inferior  obliques  than  by  the 
superior. 

No  test  for  orthophoria  is  complete  until  the  verting- 
power  of  the  recti  has  been  determined. 

In  the  study  of  the  field  of  fixation,  or,  better,  the  field 
of  rotations,  it  must  not  be  confounded  with  the  field  of 
vision  which,  in  healthy  eyes,  is  much  larg-er  than  the 
former.  The  rotations  in  the  four  cardinal  directions 
are  those  to  be  studied;  and  the  best  means  at  our  com- 
mand for  this  study  is  the  tropometer,  invented  by  Stev- 
ens. A  fair  degree  of  accuracy  may  be  obtained  by  the 
use  of  the  perimeter  and  a  lighted  candle,  or  a  small 
electric  lig"ht,  in  a  dark  room.  This  method,  though  not 
the  better  of  the  two,  will  be  described  first.  The  pa- 
tient should  be  placed  in  front  of  the  perimeter  as  for 
the  taking-  of  the  field  of  vision.  The  eye  to  be  tested 
must  be  in  the  center  of  the  perimeter  curve.  The  ex- 
tent of  the  outward  rotation  is  determined  by  asking-  the 
patient  to  fix  the  blaze  of  a  small  candle,  or  a  small  elec- 
tric light,  as  it  is  moved  behind  the  arm  of  the  perimeter, 
toward  the  temporal  side  of  the  eye  under  test.  When 
the  patient  can  turn  the  eye  no  further  out,  the  operator 
putting-  his  open  eye  (one  eye  should  be  closed)  in  line 
with  the  candle  and  the  center  of  the  rotated  cornea,  ob- 
serves the  imag-e  of  the  candle  reflected  from  the  center 


ORTHOPHORIA.  169 

of  the  cornea,  and  then  reads  the  number  of  degrees 
marked  at  the  point  of  location  of  the  candle.  In  like 
manner  the  extent  of  rotation  of  the  same  eve  in  the  op- 
posite direction  is  determined  and  noted.  The  arms  of 
the  perimeter  are  now  to  be  placed  in  the  vertical  posi- 
tion, when  the  extent  of  the  upward  and  downward  ro- 
tations can  be  measured  in  the  same  way.  There  is  no 
necessity  for  other  than  these  measurements  in  the  four 
cardinal  directions.  Muscles  found  capable  of  making 
these  rotations  reach  the  standard,  will  be  fully  capable 
of  doing  the  work  of  effecting  any  other  rotation,  which, 
after  all,  must  be  a  combination  of  the  forces  effecting 
the  cardinal  rotations.  Both  eyes  should  be  thus  tested. 
The  Stevens  tropometer,  shown  in  the  accompany- 
ing cut,  Fig.  34,  is  an  instrument  of  greater  precision 
and  is  more  convenient  for  use.  The  arrangement  for 
fixing  the  head  needs  no  description,  since  it  is  easil}7  un- 
derstood. At  the  base  of  the  instrument  is  a  thumb- 
screw by  means  of  which  the  tropometer  proper  can  be 
placed  at  varying  distances  from  the  patient's  eye.  The 
object  of  this  arrangement  is  to  so  adjust  the  instrument 
that  the  reflected  image  of  the  cornea  will  extend  from 
one  of  the  darker  lines  in  the  scale,  to  the  other  one,  and 
this  adjustment  should  be  made  at  the  beginning  of 
every  examination.  Near  the  center  of  the  upright  piece 
there  is  a  thumb-screw  for  elevating  or  depressing  the 


170 


ORTHOPHORIA. 


Fig-  34- 


mirror  so  that  its  center  may  be  on  a  level  with  the  pa- 
tient's eye.  At  the  top  of  this  upright  there  is  a  flat  base 
by  means  of  which  the  mirror-box  of  the  tropometer  may 
be  placed  directly  in  front  of  the  eye  to  be  examined. 
This  is  effected  by  simply  sliding  the  tropometer  in 
either  the  one  direction  or  the  other.  The  horizontal 
part  of  the  tropometer  is  a  little  more  difficult  to  under- 
stand, and  yet  it  is  simplicity  itself.  It  consists  of  a 
square  box,  closed  completely  by  metal  on  all  sides  ex- 
cept the  one  facing  the  patient,  and  in  the  center  of  this 


ORTHOPHORIA.  17l 

side  is  an  opening*  which  is  filled  with  a  disc  of  perfectly 
plane  transparent  glass,  in  the  center  of  which  is  a 
white  dot  at  which  the  patient  is  directed  to  look,  at  the 
beginning  of  the  examination.  Inside  of  this  box  is  the 
mirror,  placed  at  an  angle  of  45°  on  a  vertical  axis. 
From  this  mirror  the  patient's  eye  is  reflected,  an  aerial 
image  of  which  is  formed  on  the  graduated  disc,  so  that 
the  operator  at  the  other  end  of  the  instrument  may  see 
it.  The  sharpness  of  the  image  is  regulated  by  the 
thumb-screw  in  the  center  of  the  telescope  part,  by 
means  of  which  the  lenses  contained  in  the  tube  are  so 
adjusted  as  to  enable  the  operator  to  get  perfect  sharp- 
ness of  outline  of  the  aerial  image.  The  disc  containing 
the  graduated  scale  has  been  constructed  with  mathe- 
matical correctness.  In  the  center  of  this  disc  there  is  a 
heavy  line  extending  entirely  across.  At  right-angles  to 
this  base-line  there  extends  from  each  side  a  heavy  line, 
the  distance  between  the  two  being  nearly  60°.  On 
either  side  of  the  base-line  there  are  lighter  lines  placed 
at  points  10°  apart.  When  the  handle  of  this  disc  is 
vertical,  the  position  is  for  measuring  superversion  and 
sub-version.  With  this  instrument  adjusted  so  the  pa- 
tient's cornea  extends  from  one  heavy  line  to  the  other, 
the  base-line  passing  down  through  the  center  of  the 
cornea,  and  the  image  itself  being  sharply  focused,  we 
take  the  superversion  by  asking  the  patient  to  look  up  as 


172  ORTHOPHORIA. 

far  as  possible.  In  the  reflected  image  the  eye  appears 
to  move  downward,  for  the  image  is  irverted.  The  po- 
sition of  the  lower  margin  of  the  cornea  (upper  of  image; 
is  now  noted  and  the  extent  of  the  rotation  is  read  off  on 
the  scale.  In  a  normal  condition  the  superversion  should 
be  33°.  This  having  been  noted,  the  patient  is  asked  to 
look  straight  forward  again,  when  the  image  of  the  cor- 
nea will  extend  from  one  heavy  line  to  the  other  as  be- 
fore, while  the  base-line  will  pass  directly  down  through 
the  center  of  the  pupil.  Now  the  patient  is  asked  to  look 
down  as  far  as  possible.  Unless  the  upper  lid  is  held  up 
by  external  force,  it  will  so  cover  the  cornea  that  the 
measurement  cannot  possibly  be  taken.  An  assistant  is 
necessary  then  to  elevate  the  upper  lid  in  order  that  sub- 
version may  be  taken.  While  the  patient  is  looking 
down  as  far  as  possible,  the  position  of  the  upper  margin 
of  the  cornea  (lower  as  it  appears  in  the  image)  is  noted, 
and  the  extent  of  the  rotation  is  read  off  on  the  scale. 
This  should  be  about  50°.  The  superversion  and  sub- 
version having  been  taken,  the  handle  connected  with  the 
scale-disc  is  turned  from  the  vertical  to  the  horizontal. 
Now  the  instrument  must  be  so  adjusted  that  the  base- 
line will  coincide  with  the  horizontal  meridian  of  the  cor- 
nea, while  the  cornea  itself  extends  from  one  heavy  line 
to  the  other.  If  the  left  eye  be  under  test,  abversion  is 
taken  by  asking  the  patient  to  look  as  far  towards  the 


ORTHOPHORIA.  173 

left  as  possible.  The  location  of  the  nasal  margin  of  the 
cornea,  when  the  eye  is  in  extreme  abversion,  is  noted  on 
the  scale  and  the  extent  of  the  rotation  is  read  off.  This 
should  be  about  50°.  This  done,  the  patient  is  asked  to 
look  straight  forward,  when  the  instrument  is  adjusted 
as  before.  Now  he  is  asked  to  look  as  far  towards  the 
right  as  possible,  when  the  extent  of  the  adversion  can 
easily  be  determined.  This  should  be  about  50°.  The 
power  of  rotation  in  the  four  cardinal  directions  having 
been  found  normal,  it  would  be  correct  to  conclude  that 
rotation  in  any  one  of  the  oblique  directions  would  also 
be  normal.  Any  marked  variations  in  the  different  ver- 
sions from  the  standard,  as  noted  above,  should  be  con- 
sidered a  very  important  guide  as  to  any  surgical  pro- 
cedure to  be  resorted  to,  but  this  will  be  more  clearly  set 
forth  in  the  study  of  heterophoria.  Both  eyes  should  be 
thus  tested. 

The  candle  method  of  simply  watching  the  eye  as  it 
rotates  in  each  of  the  four  cardinal  directions,  does  not 
commend  itself  as  being  at  all  accurate;  and  yet  it  is 
better  than  no  examination  to  determine  the  extent  of 
these  rotations.  Unless  the  temporal  rotation  carries 
the  outer  margin  of  the  cornea  to  the  external  canthus, 
and  the  inner  rotation  carries  the  inner  corneal  margin 
to  the  internal  canthus,  it  would  appear  that  these  rota- 
tions are  too  limited.  In  the  upward  and  downward  ro- 


174  ORTHOPHORIA. 

tations  there  are  only  the  lid  margins,  themselves  mov- 
able, to  give  us  an  approximate  judgment  as  to  their 
extent.  This  method  is  of  use  in  a  case  of  paresis  or 
paralysis,  but  it  ought  never  to  be  relied  on  for  other 
purposes. 

The  extent  of  these  rotations,  as  given  by  different 
authors,  varies  but  little.  L/andolt  makes  the  standard 
of  these  rotations  as  follows:  Out,  46°;  in,  44°;  down, 
50°;  up,  33°.  Stevens  places  the  standard  as  follows: 
Out,  48°  to  53°;  in,  48°  to  53°;  down,  50°;  up,  33°.  The 
standard  set  by  Stevens  is  probably  more  nearly  cor- 
rect. A  knowledge  of  an  excess  of,  or  deficiency  in,  these 
measurements  can  but  be  helpful  when  the  question  of  a 
muscle  operation  presents  itself.  The  rotating  power 
of  a  muscle  should  never  be  reduced  by  operation  below 
the  standard  measurement  for  that  muscle. 

The  importance  of  the  study  of  the  field  of  rotation 
should  not  lead  to  a  disregard  of  the  field  of  binocular 
fusion.  The  latter  can  be  determined  only  by  the  use  of 
prisms.  In  this  study  again,  it  is  not  important  to  find 
the  extent  of  the  field  except  in  the  four  cardinal  direc- 
tions. Authors  differ  as  to  the  extent  of  this,  while  none 
of  them  sufficiently  emphasize  its  importance,  in  the 
study  of  heterophoria.  The  accompanying  cut,  Fig.  35, 
shows  approximately  the  shape  and  size  of  this  field  of 
fusion.  When  an  image  is  displaced  by  a  prism  to  any 


ORTHOPHORIA. 


175 


point  within  the  field,  while  the  image  in  the  other  eye 
is  on  the  macula,  an  effort  at  fusion  will  be  made,  and  if 
the  muscle  that  must  respond  is  sufficiently  strong", 
fusion  will  at  once  take  place,  caused  by  such  a  rotation 
as  will  bring-  the  macula  under  the  displaced  image. 
When  the  image  is  thrown,  by  a  stronger  prism,  entirely 
outside  of  the  field  of  fusion,  the  guiding  sensation, 


RISHT 


UEFT 


Fig-  35- 


which  seems  to  reside  in  this  area  only,  will  not  call  on 
any  muscle  to  move  the  eye  for  the  purpose  of  fusion. 
The  nasal  limit  of  this  retinal  area,  as  measured  by 
a  prism  in  front  of  the  eye,  is  8°;  the  temporal  limit, 
25°;  the  upper  limit,  3°;  and  the  lower  limit,  3°.  The 
line  drawn  through  these  four  points  marks  the  entire 
boundary  of  the  field.  '  This  may  be  considered  the  nor- 
mal size  of  the  fusion  area.  In  some  cases  it  mav 


176  ORTHOPHORIA. 

appear  to  be  smaller,  while  in  still  other  cases  it  may 
be  larger. 

It  is  by  means  of  prisms  which  displace  an  image 
within  this  field  that  we  can  determine  the  fusion  power 
of  a  muscle.  This  may  be  termed  the  intrinsic  or  lift- 
ing- power  of  the  muscle.  A  determination  of  this  power 
is  important,  even  in  the  study  of  orthophoria,  but  of 
much  more  importance  in  the  study  of  heterophoria. 
A  knowledge  of  the  fusion  power,  associated  with  a 
knowledge  of  the  verting  power  of  a  muscle,  is  indis- 
pensable in  the  formation  of  a  judgment  as  to  what 
ought,  or  ought  not,  to  be  done  in  an  operative  way,  in 
any  given  case  of  heterophoria. 

The  power  of  the  recti  muscles  for  fusing  images,  ex- 
pressed in  prism  degrees,  is  for  the  internus  (adduction), 
25°;  for  the  externus  (abduction),  8°;  for  the  superior 
rectus  (superduction),  3°,  and  for  the  inferior  rectus  (sub- 
duction),  3°.  A  muscle  that  has  the  normal  fusion  power 
should  also  possess  the  normal  verting  power;  and  when 
the  one  is  abnormal  the  other  is  likely  to  be  abnormal 
also.  The  standard  of  the  fusion  power  of  the  recti 
might  safely  be  set  a  little  lower  than  that  given  above, 
for  all  except  that  of  the  internus.  A  fusion  abduction 
of  6°  and  a  sub-duction  and  superduction  of  2°  or  2.3° 
may  be  considered  as  favorable.  ' 

If  all   the  muscles  respond  correctly  to  the  diplopia 


ORTHOPHORIA.  177 

test;  if  the  duction  power  of  the  recti  and  the  obliques 
reaches  the  standard;  and  if  the  verting-  power  of  the 
recti  does  not  fail  short,  then  there  is  sthenic  ortho- 
phoria.  Such  a  patient  needs  no  help  for  his  ocular  ad- 
justments. 

ASTHENIC  ORTHOPHORIA. 

There  is  an  orthophoria  that  is  not  in  strength,  but  in 
weakness.  The  diplopia  tests  may  elicit  responses  indi- 
cating orthophoria  of  all  the  pairs  of  muscles,  but  these 
muscles  may  show  a  want  of  duction  power,  also  a  want 
of  verting  power.  Such  eyes,  though  orthophoric,  as 
judged  by  the  diplopia  tests,  cannot  be  as  strong  as  they 
would  be  if  the  muscles  were  possessed  of  full  intrinsic 
power.  If  an  externus  perfectly  balances  its  antagonis- 
tic internus  and  there  is  an  abduction  of  only  4°,  there 
must  be  a  correspondingly  low  adduction.  If  there  is 
harmony  between  the  superior  and  inferior  recti,  and 
they  show  a  superduction  and  sub-duction  of  only  1°, 
there  is  weakness  that  demands  attention.  Such  cases 
are  often  met  in  actual  practice.  The  treatment  is  ceil- 
ingf-to-floor  and  wall-to-wall  exercise.  The  method  of 

o 

carrying  out  this  exercise  is  both  simple  and  efficient. 
The  patient  is  directed  to  stand  against  one  wall  of  his 
room,  midway  between  the  walls  to  the  right  and  left. 
Having  previously  fastened,  by  pin  or  tack,  a  piece  of 
paper  on  each  wall  to  right  and  left,  at  an  angle  of  35°, 


178  ORTHOPHORIA. 

approximately,  and  on  a  level  with  his  eyes;  and  having 
placed  some  object  on  the  floor  immediately  in  front  of 
him  and  at  a  distance  equal  to  his  height,  he  must  stand 
with  his  head  erect  while  he  looks  up  at  the  ceiling  where 
it  joins  the  wall  in  front  of  him,  then  down  at  the  object 
on  the  floor,  and  so  on  for  six  or  eight  movements  in  the 
vertical  plane;  then  he  must  change  his  movements  to 
the  horizontal  plane,  looking  first  at  the  paper  to  the 
right,  then  at  the  paper  to  the  left,  and  so  on  for  six  or 
eight  movements  in  this  plane.  He  then  passes  again  to 
the  vertical  plane,  changing  the  point  of  view  rhythmic- 
ally every  three  seconds;  and,  at  regular  intervals,  al- 
ternating the  vertical  and  horizontal  movements.  He 
should  stop  the  exercise  always  short  of  fatigue,  and 
should  not  continue  it  longer  than  ten  minutes  at  a  time. 
Once  a  day  is  often  enough  to  resort  to  the  exercise. 
The  time  of  day  for  the  exercise  may  be  suited  to  the 
convenience  of  the  patient.  The  duction  power  should 
be  taken  at  intervals  of  a  few  weeks,  and  the  exercise 
should  be  continued  until  the  recti  show  the  normal  lift- 
ing power.  In  this  way  an  asthenic  orthophoria  may 
be  converted  into  a  sthenic  orthophoria. 

The  alternate  contraction  and  relaxation  of  the  recti, 
under  the  stimulus  of  the  first,  second,  fourth,  and  fifth 
conjugate  innervations,  if  not  carried  to  excess,  can  re- 
sult only  in  the  up-building  of  the  muscles.  Since  every 


ORTHOPHORIA.  179 

muscle  is  exercised  in  the  same  way  and  to  the  same  ex- 
tent as  its  antagonist,  there  is  no  danger  of  interfering 
with  the  equal  balance  that  existed  between  the  muscles 
before  the  exercise  was  commenced. 

There  are  cases  in  which  there  is  a  sthenic  lateral 
orthophoria  and  an  asthenic  vertical  orthophoria.  In 
such  cases  the  ceiling-to-floor  exercise  alone  should  be 
advised.  There  are  other  cases  in  which  there  is  a 
sthenic  vertical  orthophoria  and  an  asthenic  lateral 
orthophoria.  In  these  cases  only  the  wall-to-wall  ex- 
ercise should  be  given. 

Since  the  strength  of  opposing  muscles  is  correspond- 
ingly increased,  there  is  never  any  danger  of  accomplish- 
ing too  much.  A  lateral  orthophoria  with  an  abduction 
of  12°  and  an  adduction  of  36°,  is  a  better  condition  than 
when  the  abduction  is  8°  and  the  adduction  is  25°.  A 
vertical  orthophoria  with  sub-duction  and  superduction 
of  5°  is  better  than  if  these  ductions  were  only  3°. 

The  diagnosis  between  sthenic  and  asthenic  ortho- 
phoria should  always  be  made. 


CHAPTER  III. 


HETEROPHORIA. 


Heterophoria  is  a  generic  term  and  includes  all  errors 
of  tendency  of  all  the  extrinsic  ocular  muscles.  It  is  the 
disposition  on  the  part  of  a  muscle,  or  muscles,  to  dis- 
obey the  law  governing  it;  that  is,  the  supreme  law  of 
corresponding-  retinal  points.  To  obey  this  law,  the 
recti,  in  the  final  result  of  their  action,  are  concerned  only 
with  the  visual  axes;  the  superior  and  inferior  recti  of 
the  two  eyes  keeping  these  axes  in  the  same  plane,  the 
external  and  internal  recti  causing-  them  to  intersect  at 
the  point  of  fixation.  The  obliques  must  keep  the  verti- 
cal axes  of  the  eyes  parallel  with  each  other  and  with 
the  median  plane  of  the  head.  In  orthophoria  the  de- 
mands of  this  law  are  easily  met;  in  heterophoria  the  de- 
mands are  met,  but  not  with  ease;  there  is  strain  or 
overwork. 

In  heterophoria  involving-  the  superior  and  inferior 
recti,  there  is  a  disposition  on  the  part  of  these  muscles 
not  to  keep  the  visual  axes  in  the  same  plane,  the  visual 
axis  of  one  eye  tending-  above  the  plane  that  ought  to  be 
common  to  the  two  axes,  while  the  visual  axis  of  the 

(180) 


HETEROPHORIA.  181 

other  eye  has  a  corresponding-  tendency  downward.  The 
direction  of  this  tendency  gives  name  to  the  error:  up- 
ward tendency,  hyperphoria;  downward  tendency,  cata- 
phoria.  In  heterophoria  involving  the  lateral  recti,  there 
is  a  tendency  toward  intersection  of  the  visual  axes  be- 
tween the  observer  and  the  point  observed,  or  they  tend 
to  intersect  beyond  the  point  of  view,  or  even  to  become 
divergent.  The  tendency  to  cross  too  soon  is  esophoria; 
the  tendency  to  cross  too  far  away  is  exophoria.  In 
heterophoria  involving  the  obliques,  there  is  either  a 
tendency  on  the  part  of  the  inferior  obliques  to  cause 
the  vertical  axes  to  diverge  from  each  other  above,  or  of 
the  superior  obliques  to  converge  these  above.  The  for- 
mer is  properly  termed  -plus  cyclop Jioria;  the  latter, 
minus  cyclophoria. 

Heterophoria  has  its  causes,  and  just  as  certainly  has 
its  consequences.  To  exist  in  any  one  of  its  several 
forms,  one  muscle  must  have  an  advantage  over  its  an- 
tagonist; or,  what  is  the  same  thing,  in  reverse  order, 
one  muscle  must  be  at  a  disadvantage  as  compared  with 
its  antagonist.  The  difference  may  be  in  the  compara- 
tive sizes  of  the  two  muscles,  the  one  being  larger,  and, 
therefore,  stronger  than  the  other.  There  may  be  a 
difference  in  the  insertions  of  the  two  muscles,  the  one 
being  too  near  the  corneo-scleral  junction  and  the  other 
too  far  back.  These  muscles  may  be  of  proper  size,  but 


182  HETEROPHORIA. 

it  is  certain  that  the  one  with  insertion  too  far  forward 
will  exert  more  power  in  rotating  the  globe  than  its  an- 
tagonist not  so  favorably  attached.  It  must  also  be 
conceded  as  possible  that  one  muscle  of  proper  size  as 
compared  with  its  antagonist,  and  with  no  more  favor- 
able attachment,  is  more  powerful  than  its  antagonist 
because  of  an  excess  of  nerve  impulse  sent  to  it.  Wheth- 
er the  one  cause  exists  alone,  or  whether  two  or  more  of 
them  combine  in  the  production  of  heterophoria,  the 
error  is  corrected  by  an  extraordinary  nerve  impulse 
which  is  sent  to  the  weaker  muscle  of  a  pair,  and  thus, 
with  the  undue  expenditure  of  nerve  force,  binocular 
single  vision  is  maintained. 

ORBITAL  MALFORMATIONS. 

As  has  been  claimed  by  Stevens,  Risley,  and  others, 
malformation  of  the  orbits  may  be  a  cause  of  heteropho- 
ria. Such  malformation  can  be  the  direct  cause  of 
vertical  and  lateral  errors,  but  not  of  errors  of  the 
obliques.  As  is  shown  in  Chapter  I.,  ideally-con- 
structed orbits  are  such  that  the  eyes  they  contain, 
when  in  the  primary  positions,  will  have  their  horizon- 
tal planes  lie  in  the  fixed  horizontal  plane  of  the  head. 
As  already  defined,  this  fixed  horizontal  plane  must  nec- 
essarily be  at  right-angles  to  the  median  plane  of  the 
head.  It  may  be  said  always  to  pass  through  the  optic 


HETEROPHORIA.  183 

chiasm.  Thence  anteriorly  it  should  pass  through  the 
centers  of  origin  of  the  extern!  and  interni  of  both  eyes; 
thence  on  through  the  centers  of  rotation  of  the  two 
eyes.  Posteriorly  this  plane  passes,  approximately,  be- 
tween the  cerebrum  and  cerebellum,  just  as  the  median 
plane  of  the  head  passes  between  the  two  halves  of  the 
cerebrum. 

In  the  chapter  on  hyperphoria  and  cataphoria  will  be 
found  illustrations  showing  how  an  orbit  that  is  too  low 
will  contain  a  cataphoric  eye,  while  an  orbit  that  is  too 
high  will  contain  a  hyperphoric  eye. 

If  the  two  orbits  are  neither  too  high  nor  too  low,  but 
only  too  far  apart  or  too  close  together,  it  is  hard  to  see 
how  any  form  of  heterophoria  could  result;  yet  it  is  pos- 
sible that  a  lateral  error  might  be  thus  caused:  an  ex- 
ophoria  when  the  eyes  are  too  far  apart,  an  esophoria 
when  they  are  too  close  together. 

However  interesting  may  be  the  study  of  malforma- 
tion of  the  orbits  as  causative  of  heterophoria,  the  treat- 
ment, whether  operative  or  otherwise,  must  be  directed 
to  the  muscles;  since  it  would  be  utterly  impossible,  by 
manipulation  or  operation,  to  convert  a  malformed  orbit 
into  an  ideal  one.  It  stands  to  reason  that  prisms  in  po- 
sitions of  rest  would  be  the  ideal  treatment  of  hetero- 
phorias  dependent  on  orbital  malformation,  there  being 
no  muscle  imbalance  -per  se. 


184  HETEROPHORIA. 

To  Stevens,  of  New  York,  is  due  much  credit  for  his 
pioneer  work  in  the  study  of  the  ocular  muscles.  Be- 
fore him,  Graefe,  in  his  study  of  insufficiency  of  the  in- 
terni,  gave  us  a  glimpse  of  that  light  which  Stevens  af- 
terwards turned  on  more  fully.  By  means  of  the  pho- 
rometer  which  he  invented,  he  found  it  much  easier  to 
investigate  the  recti  muscles.  He  prosecuted  this  study 
for  many  years,  almost  alone,  and  under  fire  of  most  se- 
vere criticism.  The  information  given  us  by  Graefe 
about  insufficiency  of  the  recti  muscles  is  so  incomplete, 
as  compared  with  the  results  of  Stevens'  labors,  that 
the  latter  may  well  be  looked  upon  as  the  discoverer  of 
these  conditions.  The  remarkable  feature  of  Stevens' 
work  is  that  he  so  long  ignored  any  study  of  the  oblique 
muscles,  which  have  a  duty  to  perform  no  less  impor- 
tant and  exacting  than  that  required  of  the  recti.  It 
has  already  been  shown  that  the  obliques,  under  the  in- 
fluence of  four  conjugate  innervations,  must  keep  the 
vertical  axes  of  the  eyes  parallel  with  each  other  and 
with  the  median  plane  of  the  head.  As  far  back  as 
1891,*  it  was  shown  that  the  obliques  were  not  always 
capable  of  accomplishing  their  work  with  ease;  and  a 
little  later  the  method  of  exercising  these  muscles  so  as 
to  strengthen  them,  was  introduced. t  In  1893  it  was 

*  See  Archives  of  Ophthalmology,  Vol.  XX.,  No.  1. 
t  See  Ophthalmic  Record,  Vol.  II.,  No.  1. 


HETEROPHORIA.  185 

shown  that  one  danger  attending  an  advancement  of  a 
rectus  muscle  was  that  its  new  attachment  might  be  so 
displaced  as  to  throw  unbearable  work  on  one  or  other  of 
the  obliques.*  Again,  in  1893,  following-  a  suggestion  by 
Swan  M.  Burnett  that  one  or  more  of  the  recti  might 
naturally  be  so  attached  that  the  obliques  would  be  in- 
sufficient for  the  work  demanded  of  them,  an  operation 
on  a  rectus  for  strengthening  an  oblique  muscle  was 
suggested. t  It  was  not  until  1895  or  1896  that  Stevens 
commenced  his  study  of  the  obliques.  Soon  thereafter 
he  invented  his  clinoscope,  the  capabilities  of  which  will 
be  fully  shown  in  the  discussion  of  c}Tclophoria.  His 
work  in  this  direction,  as  might  have  been  expected,  has 
been  helpful;  but  in  his  paper  published  in  the  January 
(1899)  number  of  the  Archives  of  Ophthalmology,  he 
claims  entirely  too  much  credit  for  himself,  as  expressed 
in  these  words:  "Anomalous  declinations  not  related  to 
disabilities  of  the  muscles  had,  previous  to  my  own  con- 
tributions, t  obtained  no  recognition  as  a  practical  sub- 
ject, if,  indeed,  it  had  been  recognized  at  all,  although  it 
is  probably  one  of  the  most  practical  of  the  various  im- 
portant phases  of  the  adjustments  of  the  eyes." 

In  the  matter  of  nomenclature  Stevens  gave  us  per- 
fect terms,  but  not  a  complete  list.     There  should  be  a 

*  See  Ophthalmic  Record,  Vol.  II.,  No.  9. 

f  See  New  Truths  in  Ophthalmology,  1893,  pp.  40.  41. 

t  Not  earlier  than  1897. 


186  HETEROPHORIA. 

name  for  every  deviating  tendency,  but  he  gave  none  for 
the  downward  tendency.  In  conformity  with  his  nomen- 
clature, the  downward  tendency  of  an  eye  has  been  named 
cataphoria.* 

Before  Stevens  began  the  study  of  the  obliques,  the 
name  cyclophoria  was  given  to  insufficiency  of  the  ob- 
liques, in  conformity  with  the  nomenclature  applied  to 
the  recti.  To  distinguish  insufficiency  of  the  superior 
from  insufficiency  of  the  inferior  obliques,  the  term  plus 
cyclophoria  has  been  applied  to  the  former  and  minus 
cyclophoria  to  the  latter.  Maddox,  for  some  reason, 
preferred  the  terms  plus  torsion  and  minus  torsion. 
Still  later  Stevens  gives  to  these  conditions  the  names 
plus  declination  and  minus  declination.  Unless  there  is 
a  very  special  reason  for  doing  otherwise,  there  should 
be  uniformity  in  the  nomenclature  applied  to  the  ocular 
muscles.  As  there  appears  no  valid  reason  against  this 
uniformity,  the  term  cyclophoria  alone  will  be  used  in 
the  chapter  on  errors  of  the  obliques. 

Terms  should  be  multiplied  only  when  there  is  abso- 
lute need  for  them.  The  terms  anaphoria  and  katapho- 
ria  added  to  nomenclature  by  Stevens  a  while  ago,  and 
applied,  respectively,  to  an  upward  tendency  of  both  eyes 
and  the  reverse,  a  downward  tendency  of  both  eyes, 
would  tend  only  to  confusion.  These  conditions  exist, 

*  See  New  Truths  in  Ophthalmology,  1893,  page  68. 


HETEROPHORIA.  187 

but  it  is  far  better  to  say  double  kyperphoria  and  double 
cataphoria. 

Maddox  did  good  work  when  he  offered  as  substitutes 
for  sursum  -  duction  and  deorsum  -  duction  the  simpler 
and  easier  terms  super-duction  and  sub-duction.  But 
even  these  terms  should  be  given  only  a  single  meaning. 
They  should  be  made  to  apply  only  to  the  power  the 
superior  and  inferior  recti  have  for  overcoming  prisms 
in  the  interest  of  binocular  single  vision.  Likewise  ad- 
duction and  abduction  should  be  restricted  in  meaning  so 
as  to  apply  only  to  the  interni  and  externi  in  their  ef- 
forts to  overcome  the  lateral  displacing  of  images  by 
prisms. 

The  fact  that  it  is  better  to  have  two  terms,  each 
with  a  single  meaning,  than  to  have  one  term  with  two 
very  different  applications,  must  be  the  author's  apol- 
ogy for  adopting  the  following  nomenclature  for  the 
turning  of  the  eyes  in  the  four  cardinal  directions:  Ab- 
version,  turning  the  eye  out;  adversion,  turning  the  eye 
in;  superversion,  turning  the  eye  up;  and  sub-version, 
turning  the  eye  down.  These  terms  are  shorter  and  bet- 
ter than  outward  rotation,  inward  rotation,  upward  rota- 
tion, and  downward  rotation. 

Duane  deserves  credit  for  his  very  careful  study  of 
the  ocular  muscles  in  his  little  brochure,  ' '  Motor  Anom- 
alies of  the  Eye; "  but  the  terms  hyperkinesis  and  hypo- 


188  HETEROPHORIA 

kinesis,  introduced  by  him,  are  not  nearly  so  simple  or 
easy  as  the  terms  sthcnic  and  asthenia  esophoria,  sthenic 
and  asthenic  exophoria,  and  sthenic  and  asthenic  hyper- 
phoria, and  so  on  for  all  the  phorias.  The  meaning", 
however,  is  precisely  the  same. 

The  heterophoria  that  is  purely  innervational  should 
be  designated  by  the  prefix  pseudo  as  pseudo-esophoria, 
a  condition  depending*  on  the  relationship  existing-  be- 
tween accommodation  and  convergence,  and  not  depend- 
ent on  any  error  inherent  in  the  interni. 

The  following-  is  a  list  of  the  heterophorias: 

(1)  Esophoria,  of  which  there  are  two  varieties,  viz.: 
pseudo-esophoria  and  intrinsic  esophoria.     Of  the  intrin- 
sic variety  there  are  two  kinds,  sthenic  and  asthenic. 

(2)  Exophoria,  pseudo  and  intrinsic.     Of  the  intrinsic 
variety  there  are  two  kinds,  sthenic  and  asthenic. 

(3)  Hyperphoria  and  cataphoria,  which  are  always  in- 
trinsic when  the  superior  and  inferior  recti  are  the  only 
factors.     These  errors  are  either  sthenic  or   asthenic. 
There  is  now  and  then  to  be  found  a  double  hyperphoria 
or  a  double  cataphoria. 

(4)  Cyclophoria,  plus  and  minus,  both  pseudo  and  in- 
trinsic.    The  intrinsic  variety  may  be  either  sthenic  or 
asthenic. 

Two  or  three  of  these  errors  may  be  found  combined 
in  many  cases;  but  it  is  probably  better  not  to  have 


HETEROPHORIA.  189 

compound  names  for  such  combinations  of  errors,  as  it  is 
important  that  the  quantity  of  each  error  should  be 
noted.  It  would  be  difficult  to  indicate  the  quantity  of 
the  two  errors  if  the  note  was  made  hyper-esopohria  or 
hyper-cyclophoria. 

TESTS. 

There  are  some  interesting  tests  for  heterophoria  that 
can  be  made,  in  a  rough  way,  independent  of  the  pho- 
rometer.  One  is  the  cover  test.  If  there  is  an  error  of 
any  magnitude,  it  will  manifest  itself  on  covering  one 
eye  while  the  patient  is  looking  with  both  eyes  at  a  test 
object  twenty  feet  distant.  The  covered  eye  will  imme- 
diately place  itself  in  a  state  of  equilibrium.  When  the 
cover  is  removed,  it  will  return  to  the  position  of  har- 
mony with  the  fellow  eye.  This  readjustment  can  be 
easily  seen,  in  many  cases,  by  the  observer.  The  direc- 
tion in  which  the  eye  moves  when  uncovered  indicates 
the  kind,  but  not  the  quantity,  of  the  heterophoria.  A 
patient  of  keen  observation  will  be  made  conscious  of 
the  disturbance.  This  is  better  done  by  covering  and 
uncovering  the  eyes  alternately.  In  high  degrees  of 
heterophoria  a  plane  red  glass  placed  before  one  eye 
will  suspend,  to  some  extent,  the  effort  at  fusion,  and 
diplopia  will  result.  A  candle  should  now  be  the  test 
object.  The  position  of  the  red  blaze,  the  patient  the 


190  HETEROPHORIA. 

while  looking-  at  the  real  candle,  will  indicate  the  kind 
of  error.  Only  the  higher  errors  respond  to  the  red- 
glass  test. 

The  test  by  means  of  the  phorometer,  preferably  the 
monocular  instrument,  for  the  reasons  given  in  the 
chapter  on  orthophoria,  is  the  only  one  to  be  relied 
upon.  By  it  the  kind  of  error  is  quickly  determined 
and  the  quantity  is  easily  measured.  In  testing  the 
interni  and  externi,  the  6°  prism  is  placed,  base  up, 
in  the  cell  next  to  the  eye.  This  will  throw  the  false 
image  above  on  the  retina  and  entirely  outside  the  field 
of  binocular  fusion,  so  that  no  attempt  can  be  made  at 
fusion.  The  false  object  will  be  below  the  true,  and 
will  bear  that  relationship  to  it  determined  by  the  exist- 
ing imbalance.  The  handle  of  the  rotary  prisms  must 
be  horizontal,  the  index  at  zero,  and  the  instrument  per- 
fectly level.  The  true  object  must  be  the  one  looked  at. 
If  the  false  object  is  toward  the  opposite  side,  there  is 
exophoria.  Turning  the  controlling  screw,  the  index  is 
moved  toward  the  corresponding  side  until  the  patient 
says  the  false  object  is  directly  under  the  true.  The 
number  at  which  the  index  stands  marks  the  quantity  of 
exophoria  for  that  eye. 

If  the  false  object,  instead  of  being  on  the  opposite 
side,  shows  itself  on  the  corresponding  side,  the  existing 
error  is  esophoria.  The  controlling  screw  is  now  turned 


HETEROPHORIA.  191 

so  that  the  index  moves  toward  the  opposite  side.  The 
revolution  is  stopped  when  the  patient  says  the  false  ob- 
ject is  in  a  vertical  line  with  the  true  one.  The  number 
at  which  the  index  stands  shows  the  quantity  of  esopho- 
ria  for  that  eye. 

The  test  having  been  made  for  the  distance,  it  should 
now  be  repeated  at  the  reading-  point.  The  test  object 
now  should  be  a  white  card  in  the  center  of  which  is  a 
black  dot,  and  the  card  should  be  held  directly  in  front 
of  the  eyes.  There  should  be  no  line  drawn  vertically 
throug-h  the  dot,  as  advised  by  Graefe,  for  the  reason 
that  this  line  would  cross  the  area  of  binocular  fusion, 
and  would  thus  lead  to  an  attempt,  on  the  part  of  the 
eye,  to  correct  its  error.  The  kind  of  error  is  deter- 
mined and  its  quantity  is  measured,  as  in  the  distant 
test.  The  result,  not  always  the  same  as  found  in  the 
distant  test,  should  be  noted. 

The  lateral  error  having-  been  thus  found  and  meas- 
ured, the  6°  prism  should  be  removed  and  the  10°  prism, 
base  toward  the  nose,  should  be  placed  in  the  cell;  the 
handle  of  the  rotary  prism  should  be  placed  vertically, 
and  the  index  must  be  made  to  stand  at  zero.  It  is  now 
of  vast  importance  that  the  instrument  shall  be  perfect- 
ly level;  otherwise,  a  vertical  error  may  be  shown  when 
none  exists.  The  instrument  thus  adjusted,  any  verti- 
cal imbalance  may  be  detected  and  measured.  As  in  the 


192  HETEROPHORIA. 

test  for  lateral  errors,  the  true  object  must  be  the  one 
fixed.  The  false  image  will  be  thrown  outside  the  area 
of  binocular  fusion,  toward  the  nose,  while  the  false  ob- 
ject will  appear  on  that  side  of  the  true,  corresponding 
to  the  eye  under  test.  If  the  false  object  is  below  the 
horizontal  line  passing"  through  the  true,  there  is  hyper- 
phoria  of  that  eye,  the  quantity  of  which  is  determined 
by  revolving  the  controlling-  screw  so  that  the  index 
shall  move  upward.  The  number  at  which  the  index 
stands  when  the  patient  says  the  two  objects  are  level 
shows  the  quantity  of  the  error. 

If  in  the  test  the  false  object  is  above  the  horizontal 
line  passing  through  the  true,  there  is  cataphoria  of 
that  eye.  The  screw  is  now  turned  so  that  the  index 
shall  move  downward.  The  number  at  which  the  index 
stands,  when  the  patient  says  the  objects  are  level, 
shows  the  quantity  of  the  cataphoria.  The  test  for  ver- 
tical imbalance  need  not  be  repeated  at  the  near  point. 

The  one  eye  having  been  tested  thus  for  imbalance  of 
all  the  recti,  the  instrument  should  now  be  turned  into 
position  before  the  fellow  eye,  that  the  lateral  and  ver- 
tical imbalances  it  may  have  may  be  found  and  measured. 
Usually,  if  there  is  esophoria  of  one  eye,  the  other  will 
also  show  esophoria;  the  amount  in  the  one  is  about 
equal  to  that  in  the  other.  Occasionally,  however,  there 
will  be  a  difference  of  1°  or  even  more.  The  same  may 


HETEROPHORIA.  193 

be  said  of  exophoria.  When  there  is  hyperphoria  of  one 
eye,  the  other  is  usually  cataphoric,  and  the  one  error  is 
about  equal  to  the  other. 

A  double  hyperphoria  and  a  double  cataphoria  cannot 
so  easily  be  shown,  in  the  imbalance  test,  by  the  phorom- 
eter.  The  proof  test,  which  is  by  means  of  the  Mad- 
dox  double  prism,  quickly  shows  either  of  these  errors 
when  they  exist.  The  base-line  of  these  prisms  (4°) 
should  be  held  horizontally  before  first  one  eye  and  then 
the  other,  having-  each  eye  look  at  the  distant  test  ob- 
ject, first  through  the  upper  prism  and  then  through 
the  lower,  observing-  that  position  which  throws  the 
double  objects  closer  tog-ether.  If  they  are  closer  for 
both  eyes  when  the  false  object  is  seen  through  the 
upper  prism,  there  is  double  hyperphoria;  but  if  the}" 
are  closer  for  both  eyes  when  the  false  object  is  seen 
through  the  lower  prism,  there  is  double  cataphoria. 

It  can  be  readily  understood  that,  if  there  is  hyper- 
phoria of  one  eye  and  cataphoria  of  the  other,  the  two 
objects  will  be  closer  together  when  the  false  one  is 
seen,  by  the  hyperphoric  eye,  through  the  upper  prism, 
and  by  the  cataphoric  eye  when  seen  through  the  lower 
prism.  Hence  the  reason  for  calling  this  use  of  the 
double  prism  the  proof  test  of  hyperphoria  and  cata- 
phoria. 

The  next  step  in  the  testing  is  to  determine  the  ability 


194  HETEROPHORIA. 

of  the  obliques  to  parallel  the  vertical  axes  of  the  eyes 
with  the  median  plane  of  the  head.  This  can  be  done 
rudely  in  any  one  of  several  ways :  First,  by  means  of 
the  Maddox  double  prism,  the  object  looked  at  being-  a 
horizontal  line  on  a  blackboard,  twenty  feet  distant,  or 
a  horizontal  line  on  a  card  held  at  the  reading-  distance; 
preferably,  both.  The  base-line  of  the  double  prism 
(4°)  should  be  horizontal  and  so  held  before  one  eye  as  to 
double  the  test-line.  The  two  lines  seen  by  this  eye 
must  be  parallel.  The  third  line,  seen  by  the  other  eye, 
should  be  between  the  other  two  and  parallel  with  them. 
A  dipping-  of  the  true  line  toward  the  opposite  side 
would  show  a  plus  cyclophoria,  while  a  dipping-  toward 
the  corresponding  side  would  show  a  minus  cyclophoria. 
The  quantity  of  the  error  thus  shown,  however,  cannot 
be  measured. 

The  same  test  may  be  made  by  means  of  a  sing-le 
prism  of  4°,  base  up  or  down,  before  the  eye;  but  even 
still  more  easily  it  may  be  made  by  the  revolving-  prism 
in  position  for  taking-  the  sub-ducting  and  superducting 
power.  The  rotation,  of  course,  must  be  carried  beyond 
the  possibility  of  fusion.  The  false  line  is  seen  by  the 
eye  before  which  the  single  prism  is  held  or  the  rotary 
prism  has  been  placed,  while  the  true  line  is  seen  by  the 
other  eye.  The  refracting  angle  of  the  prism  points  in 
the  direction  of  the  false  line.  When  this  line  is  seen 


HETEROPHORIA.  195 

below,  by  the  right  eye,  and  the  ends  of  the  two  toward 
the  right  converge,  there  is  plus  cyclophoria;  if  they 
diverge  toward  the  right,  then  there  is  minus  cyclopho- 
ria. There  is  no  method  of  measuring  the  error  thus 
found.  In  revolving  the  rotary  prism  or  in  turning  the 
single  prism  so  as  to  make  it  possible  for  fusion  to  take 
place,  it  is  interesting  for  the  patient  to  watch  the  man- 
ner of  fusing;  if  there  is  cyclophoria,  the  two  lines  will 
come  together  at  one  end  first  and  then  quickly  fuse 
throughout. 

The  Stevens  clinoscope  will  detect  and  measure  any 
existing  cyclophoria;  but  the  best  instrument  for  detect- 
ing cyclophoria  and  measuring  the  amount  of  the  error 
is  the  cyclo-phorometer.  It  is  much  cheaper  than  the 
clinoscope,  and,  better  still,  it  is  simpler  in  construction 
and  much  more  easily  manipulated.  The  5°  prism,  base 
up,  behind  one  rod  gives  the  second  streak  of  light;  the 
thumbscrew  makes  it  easy  to  place  the  one  streak  di- 
rectly under  the  other — ends  even.  If  the  axes  of  the 
rods  are  at  zero  and  the  two  streaks  are  not  parallel, 
cyclophoria  is  positively  shown;  if  the  lower  streak  is 
seen  by  the  left  eye  and  the  two  streaks  converge  at  the 
left,  there  is  plus  cyclophoria;  but  if  they  diverge  at  the 
left,  there  is  minus  cyclophoria.  The  extent  of  the 
turning  of  the  rod  on  the  one  side  or  the  other,  neces- 
sary for  paralleling  the  streaks,  measures  the  quantity 


196  HETEROPHORIA. 

of  the  cyclophoria.  It  is  not  necessary,  with  the  cyclo- 
phorometer,  to  keep  in  mind  the  fact  that  the  lower 
streak  is  seen  by  the  eye  that  has  the  displacing-  prism 
before  it,  for  the  position  of  the  axis  of  the  rod  at  the 
time  the  streaks  are  made  parallel  names  the  error  as 
well  as  measures  its  quantity:  when  the  axes  must  be 
moved  into  the  nasal  arc,  there  is  plus  cyclophoria;  into 
the  temporal  arc,  there  is  minus  cyclophoria. 

The  spirit  level  of  the  cyclo-phorometer  enables  one  to 
determine  if  the  cyclophoria  is  monocular  or  binocular. 
When  the  two  streaks  of  light  converge  at  one  end  or 
the  other,  if  the  error  is  binocular,  neither  of  the  lines 
will  be  horizontal.  If  one  is  horizontal  while  the  other 
is  oblique,  the  error  is  monocular;  if  both  lines  are  in- 
clined in  the  same  direction,  it  shows  plus  cyclophoria  in 
one  eye  and  minus  cyclophoria  in  the  other. 

Having-  followed  out  the  tests  already  described — the 
tests  for  imbalance — one  knows  the  kind  of  error  or  er- 
rors in  the  individual  case,  but  remains  ignorant  of  the 
character  of  these  errors.  The  duction  and  version  tests 
alone  can  reveal  the  fact  that  an  error  is  sthenic  or  as- 
thenic,  just  as  the  study  of  the  refractive  errors  alone  re- 
veals whether  or  not  a  given  heterophoria  is  pseudo  or 
intrinsic. 

The  duction  test  is  to  determine  the  power  the  mus- 
cles have  for  overcoming  the  displacing  of  images  by 


HETEROPHORIA.  197 

means  of  prisms.  To  this  meaning-  the  word  ditction, 
with  its  several  prefixes,  should  be  restricted.  The 
method  of  determining  duction  power  by  means  of  the 
monocular  phorometer  has  already  been  set  forth  in 
Chapter  II.  It  can  be  accomplished  by  means  of  the 
prisms  in  the  refraction  case,  but  not  so  quickly  nor 
so  accurately.  Duction  is  wholly  an  involuntary  act, 
and  it  is  accomplished  through  the  guiding  sensation,  in 
obedience  to  the  law  of  corresponding-  retinal  points;  but 
it  has  its  limitations.  Abduction  is  the  power  of  an 
externus  to  fuse  with  the  image  on  the  macula  of  the 
fellow  eye,  an  image  that  has  been  displaced  to  the 
nasal  side  of  the  macula  of  its  own  eye.  Less  than  6° 
of  such  power  is  subnormal;  more  than  8°  is  supernor- 
mal. Adduction  is  the  power  of  an  internus  to  move 
the  macula  outward  until  it  shall  stand  under  the  image 
that  has  been  displaced  temporally,  so  that  it  may  be 
fused  with  the  image  on  the  macula  in  the  fellow  eye. 
It  is  certainly  subnormal  if  less  than  18°  to  25°.  The 
adduction  stimulus  is  much  greater  than  any  other, 
and  is  much  more  variable.  Its  variableness  makes  it 
less  reliable  than  any  other  duction;  but,  neverthe- 
less, it  must  be  known  in  dealing  intelligently  with 
esophoria. 

Superduction  is  the  power  the  superior  rectus  has  for 
fusing  an  image  displaced  below  the  macula,  with  the 


198  HETEROPHORIA. 

image  on  the  macula  in  the  fellow  eye.  Less  than  2°  is 
subnormal;  more  than  3°  is  supernormal. 

Sub-duction  is  the  power  the  inferior  rectus  has  for 
fusing-  an  image  displaced  above  its  macula,  with  the 
image  on  the  macula  in  the  fellow  eye.  Less  than  2° 
is  subnormal;  more  than  3°  is  supernormal. 

In  all  duction  tests  it  is  better  that  the  image  should 
be  slowly  moved  away  from  the  point  occupied  by  the 
macula,  when  the  eye  is  in  the  primary  position,  toward 
the  boundary  line  of  the  field  of  binocular  fusion,  which 
should  be  considered  as  immovably  fixed.  So  long  as 
this  image  is  within  this  field  there  is  binocular  single 
vision,  for  the  macula  moves  with  the  moving  image  as 
far  as  possible;  but  the  moment  it  passes  the  border  line 
there  results  diplopia.  The  index  of  the  rotary  prism 
marks  the  duction  power  of  the  muscle  concerned.  It 
should  be  noted.  The  field  of  binocular  fusion  is  larger 
if  the  muscles  are  stronger,  smaller  if  the  muscles 
are  weaker.  Its  size  can  be  changed  both  by  exer- 
cise and  by  operations.  If  it  is  too  small,  it  may  be  in- 
creased by  exercise  and  by  shortening  and  advancement 
operations;  if  too  large,  it  can  be  reduced  only  by  tenoto- 
mies,  which  should  always  be  partial. 

Cycloduction,  which  is  involuntary,  can  be  taken  only 
by  the  clinoscope  or  the  cyclo-phorometer.  With  the  for- 
mer instrument  the  line  as  seen  by  one  eye  is  turned  by 


HETEROPHORIA.  199 

means  of  the  proper  screw  up  to  the  point  of  doubling-. 
The  index  marks  the  torsioning  power  of  the  oblique 
involved.  With  the  cyclo-phorometer  the  axis  of  one 
rod  is  moved  from  zero  toward  the  nose  to  test  the 
torsioning  power  of  the  inferior  oblique,  and  toward 
the  temple  for  determining  the  power  of  the  superior 
oblique.  An  oblique  should  have  a  fusing  power  of  from 
7°  to  10°.  The  inferior  oblique  has  a  little  greater  fusing 
power  than  the  superior  oblique. 

In  determining  the  several  ductions  the  tests  should 
be  monocular,  except  in  cycloduction. 

In  any  given  heterophoric  condition  the  duction  test, 
aided  by  the  version  test,  determines  whether  the  error 
is  sthenic  or  asthenic,  and,  therefore,  the  kind  of  opera- 
tion, if  any,  that  should  be  performed.  No  muscle  whose 
duction  power  is  normal  or  subnormal  should  be  weak- 
ened by  a  partial  tenotomy;  but  the  imbalance  should 
be  cured  either  by  a  shortening  or  an  advancement  of  its 
still  weaker  antagonist. 

No  examination  of  the  recti  muscles  is  complete  with- 
out the  taking  of  the  verting  power  of  every  one.  As 
shown  in  Chapter  II.,  this  can  be  rudely  done  by  simply 
watching  the  eyes  while  the  patient  looks  as  far  as  pos- 
sible in  the  four  cardinal  directions.  The  objection  to 
this  test  is  that  there  is  no  accuracy  in  it,  and  yet  it  is 
better  than  no  test.  The  reason  for  introducing  the 


200  HETEROPHORIA. 

terms  adversion,  abversion,  superversion,  and  sub-ver~ 
sion  has  been  given  already,  and  the  extent  of  each, 
considered  as  normal,  has  been  shown  in  the  same  con- 
nection. Of  all  instruments  for  making-  the  version 
tests,  the  Stevens  tropometer  stands  first,  because  of 
simplicity,  accuracy,  and  speed.  The  only  part  of  the 
instrument  that  should  be  dispensed  with  is  the  head 
rest,  and  this  for  two  reasons:  First,  it  interferes  with 
the  manipulation  of  the  upper  lid,  when  the  sub-version 
is  being1  taken,  for  now  the  lid  must  be  held  up  or  it 
will  entirely  obscure  the  cornea;  second,  it  obscures  too 
soon  the  small  electric  light  or  other  test  object  which 
the  patient  should  fix  as  the  superversion  is  being-  taken. 
The  mouthpiece  is  necessary  in  order  to  insure  that  the 
patient's  head  shall  not  turn  while  the  verting  power  of 
the  eye  is  being  taken. 

A  fairly  good  substitute  for  the  tropometer  is  the  per- 
imeter, if  properly  used.  There  should  be  some  means 
for  preventing  the  movement  of  the  head,  and  nothing 
could  do  this  better  than  a  mouthpiece,  such  as  consti- 
tutes a  part  of  the  tropometer.  The  eye  under  test 
should  be  in  the  center  of  the  perimeter  curve.  As  with 
the  tropometer,  the  rotations  should  be  taken  in  the 
four  cardinal  directions  only.  With  the  arms  of  the 
perimeter  in  the  horizontal  plane,  abversion  and  adver- 
sion  can  be  easily  taken;  and  if  proper  care  is  observed, 


HETEROPHORIA.  201 

the  result  will  be  practically  accurate.  The  small  elec- 
tric light,  shaded  toward  the  observer,  should  be  placed 
first  directly  in  front  of  the  eye  while  in  the  primary 
position.  From  this  position,  the  light,  while  being 
kept  in  contact  with  the  perimeter  arm,  should  be  moved 
in  the  temporal  arc — the  arc  for  abversion — slowly,  the 
patient  fixing  the  moving  light,  while  the  operator  fixes 
its  image  reflected  from  the  center  of  the  cornea,  moving 
his  own  head  harmoniously  with  the  moving  light.  The 
patient  should  speak  when  he  finds  himself  no  longer 
able  to  fix  the  light.  At  the  same  moment  the  observer 
can  see  that  the  image  is  no  longer  reflected  from  the 
center  of  the  cornea.  Thus  the  patient  serves  as  a  check 
to  the  operator,  while  the  operator  also  serves  as  a  check 
to  the  patient.  When  5°  beyond  the  point  of  fixation, 
the  small  light  becomes  so  blurred  that  the  patient  can 
easily  detect  the  change;  hence,  if  the  patient  is  closely 
observant,  there  is  small  room  for  error.  The  operator 
cannot  so  easily  detect  an  error  of  5°,  as  shown  by  the 
reflected  image.  For  these  reasons  the  subjective  part 
of  the  test  is  more  reliable  than  the  objective.  The  po- 
sition of  the  light  on  the  arc,  when  the  patient  can  no 
longer  fix  it,  and  when  the  reflected  image  begins  to  leave 
the  center  of  the  cornea,  indicates  the  degree  of  abversion. 
With  the  light  moving  along  the  nasal  arc,  adversion 
is  taken  in  like  manner,  and  its  extent  should  be  noted. 


202  HETEROPHORIA. 

With  the  arms  of  the  perimeter  rotated  into  the  ver- 
tical plane,  superversion  and  sub-version  are  taken 
by  moving*  the  light  along  the  upper  and  lower  arcs, 
respectively,  and  their  extent  is  noted.  In  taking- 
sub-version,  the  reflected  image  cannot  be  so  easily 
watched,  even  when  the  upper  lid  is  held  out  of  the 
way.  Here  the  subjective  part  of  the  test  must  be  re- 
lied upon. 

One  eye  having  been  thus  tested,  in  the  four  cardinal 
directions,  the  other  eye  should  be  properly  placed  and 
the  various  duction  powers  should  be  determined  and 
noted. 

Unlike  the  duction  power,  which  is  involuntary,  ver- 
sion power  is  a  thing  of  volition.  Neither  one  should  be 
depended  on  to  the  exclusion  of  the  other.  The  result 
of  thess  two  tests  (duction  and  version)  should  be  com- 
pounded, ir  the  surgeon  would  be  safely  guided  in  his 
operative  work,  or  even  in  the  non-operative  treatment 
of  heterophoria. 

Cycloversion  has  no  existence,  since  voluntary  rota- 
tion around  the  visual  axis  is  impossible. 

No  muscle  whose  ducting  or  verting  power  is  nor- 
mal or  subnormal  should  be  weakened  by  a  partial 
tenotomy.  No  muscle  should  be  increased  in  strength 
by  an  advancement  or  by  a  shortening  when  the  duction 
and  version  are  not  subnormal. 


HETEROPHORIA.  203 

SYMPTOMS  OP  HETEROPHORIA. 

That  there  are  cases  of  heterophoria  without  symp- 
toms must  be  conceded,  but  such  cases  are  not  often 
seen  by  the  ophthalmic  surgeon.  It  is  a  symptom,  or 
symptoms,  of  eye-strain  that  drives  the  patient  to  the 
doctor.  It  may  be  that  the  symptoms,  in  a  given  case, 
are  dependent  in  part,  if  not  wholly,  on  errors  of  refrac- 
tion; but  it  is  a  serious  mistake  to  suppose,  as  some  do, 
that  eye-strain  is  always  and  only  associated  with  the 
ciliary  muscle.  The  ciliary  muscle  is  only  one  of  eight 
muscles  connected  with  each  eye;  and  each  of  the  seven 
other  muscles,  when  called  on  to  do  abnormal  work,  is 
just  as  capable  of  developing  S3rmptoms.  People  who 
have  no  symptoms,  and  yet  have  heterophoria,  are  pos- 
sessed of  a  stable  nervous  system  and  are  physically 
strong.  The  physically  weak  and  the  nervously  unstable 
must  be  sufferers  from  eye-strain,  of  whatever  character. 
The  nervous  centers  of  the  one  may  be  compared  with 
the  steady  leaves  of  the  oak,  which  are  shaken  only  by 
a  wind;  while  the  nervous  centers  of  the  other  may  be 
compared  to  the  leaves  of  the  aspen  tree,  which  quiver 
in  the  slightest  zephyr.  Or,  again,  the  easily-disturbed 
nerve  centers  may  be  compared  to  the  leaves  of  the  trail- 
ing little  vine  seen  in  the  old  turned-out  field,  all  the 
leaves  of  which  fold  themselves  up,  if  but  one  leaf  be 
touched  by  a  human  finger. 


204  HETEROPHORIA. 

The  strong,  healthy  person,  with  a  stable  nervous 
system,  may  never  have  had  a  symptom  resulting-  from 
muscle  or  focal  errors  that  have  always  existed.  Let 
this  individual  have  an  attack  of  typhoid  fever,  measles, 
or  other  depressing  disease,  or  let  her  pass  through  a 
pregnancy  and  confinement;  now,  on  attempting  too  soon 
the  use  of  her  eyes  in  near  work,  she  begins  to  be  a  suf- 
ferer. The  suffering  becomes  a  habit,  and  she  gets  no 
permanent  relief  until  the  focal  or  muscle  error  has  been 
corrected. 

A  sudden  shock  to  a  nervous  system  that  has  been 
strong,  brings  about  a  change  that  ever  after  makes  the 
patient  feel  the  effects  of  errors  whose  existence  before 
made  no  impression. 

Growing  children,  especially  those  that  are  delicate, 
when  too  hard  pressed  in  their  school  work,  almost  in- 
variably present  some  one  of  the  many  symptoms  of 
strain.  More  women  than  men  feel  the  effects  of  muscle 
and  refractive  errors,  mainly  because  of  the  fact  that 
the  former  are  forced  to  spend  a  greater  number  of 
hours  every  day  in  near  work,  than  the  latter.  Book- 
keepers, or  men  who  are  engaged  in  other  continuous 
near  work,  are  often  forced  to  seek  aids  to  vision. 

HEADACHE. — The  most  common  of  all  the  symptoms 
caused  by  heterophoria  is  headache.  The  aching  may 
be  in  the  temple,  brow,  at  the  top  of  the  head,  over  the 


HETEROPHORIA.  205 

parietal  region,  or  in  the  back  of  the  head.  In  some 
cases  the  suffering  is  in  the  back  of  the  neck.  The  pain 
may  be  on  both  sides  of  the  head,  but  often  it  is  unilat- 
eral. It  is  periodic  in  character,  and  usually  comes  on  as 
the  result  of  prolonged,  hard  near  work.  The  headache 
which  one  has  on  awaking  in  the  morning — or,  more  prop- 
erly speaking,  the  headache  which  awakens  the  patient- 
is  usually  due  to  disturbances  in  the  sinuses,  or  cells,  that 
open  into  the  nasal  passages,  brought  about  by  mouth- 
breathing,  the  mouth-breathing  depending,  of  course,  on 
nasal  stenosis.  Rest  in  sleep  usually  relieves  the  head- 
ache of  heterophoria  and  of  refractive  errors.  Head- 
aches due  to  eye-strain,  that  come  on  unassociated  with 
near  work,  are  usually  heterophoric.  and  not  refractive. 
The  headache  that  one  has  on  bright  days  and  when 
amid  bright  surroundings,  as  the  white  buildings  and 
white  walks  of  an  exposition,  is  often  due  to  overwork 
of  a  weak  sphincter  of  the  iris,  which  is  compelled  to 
keep  the  pupil  small  that  the  retina  may  be  protected 
from  the  glare.  The  headache  of  eye-strain  is  usually 
of  the  nervous  variety — that  is,  unassociated  with  nausea 
and  vomiting.  However,  genuine  sick  headache— pure 
migraine — is  sometimes  caused  by  both  refractive  and 
muscle  errors.  The  migraine  which  disappears  as  pres- 
byopia comes  on,  proves  itself  clearly  dependent  on  an 
error  of  refraction;  and  the  same  may  be  said  of  other 


206  HETEROPHORIA. 

headaches  that  disappear  as  one  grows  old.  Indeed, 
this  coincidence  should  have  attracted  attention  to  focal 
errors  as  causative  of  headache  long-  before  any  thing- 
was  known  on  this  subject. 

Not  so  with  headaches  that  are  dependent  on  hetero- 
phoria,  for  strain  of  heterophoria  once  means  strain  of 
heterophoria  throughout  life,  unless  relieved  by  treat- 
ment, surg-ical  or  otherwise. 

VERTIGO  AND  NAUSEA. — The  kind  of  muscle  error 
that  is  the  most  common  cause  of  vertigo  and  nausea  is 
insufficiency  of  the  obliques  to  prevent  cyclophoria.  The 
correctness  of  this  teaching  is  emphasized  in  cases  of 
paresis  of  an  oblique  or  of  a  superior  or  an  inferior 
rectus,  either  one  of  which  would  be  attended  by  a  tor- 
sioning  of  the  eyes.  The  earliest  and  most  marked 
symptoms  presented  by  these  cases  are  vertigo  and  nau- 
sea, which  continue  so  long  as  the  patient  tries  to  use 
both  eyes.  Excluding  the  vision  of  the  affected  eye, 
the  symptoms  vanish.  When  cyclophoria  is  the  cause, 
these  symptoms  will  be  periodic,  and  will  present  them- 
selves only  when  the  weak  obliques  are  no  longer  able 
to  maintain  perfectly  the  parallelism  between  the  verti- 
cal axes  of  the  eyes  and  the  median  plane  of  the  head. 
Overwork,  worry,  shock,  ill  health,  sleeplessness — all 
tend  to  make  these  symptoms  worse. 

CONFUSION  OF  THOUGHT. — Any  one  of  the  hetero- 


HETEROPHORIA.  207 

phorias,  whether  associated  with  errors  of  refraction  or 
not,  necessarily  interferes  with  that  clearness  of  com- 
prehension one  would  have  if  his  eyes  were  free  from  all 
errors.  Reading  becomes  a  burden  to  heterophorics  for 
the  reason  that  their  thought  centers  work  confusedly, 
through  sympathy  with  the  motor  centers  that  are  over- 
taxed in  efforts  at  harmonizing  the  ocular  muscles.  How 
far  confusion  of  thought  may  be  carried  toward  insan- 
ity, because  of  continued  existence  of  a  muscle  error,  re- 
mains to  be  shown.  Cases  of  undoubted  insanity  have 
been  cured  by  operations  on  the  ocular  muscles.  It  has 
been  a  matter  of  common  observation  that  school  chil- 
dren who  were  counted  as  dull  and  incapable,  not  able 
to  comprehend  clearly  either  books  or  teachers,  have 
been  transformed  into  apt  scholars  by  ocular  treatment. 
In  the  race  for  an  education,  a  child  who  has  any  form 
of  heterophoria,  or  an  error  of  refraction,  is  consider- 
ably handicapped. 

CHOREA. — A  spasmodic  condition  of  the  muscles  of 
the  face — a  local  chorea — in  children  with  unstable  nerve 
centers,  is  often  caused  by  eye-strain,  as  is  shown  by 
the  quick  relief  that  follows  a  correction  of  the  condi- 
tion causing  the  strain.  The  cause  continuing  to  act, 
the  transformation  of  a  local  into  a  more  general  chorea 
is  often  effected.  It  cannot  be  denied  that  chorea,  some- 
times in  a  very  aggravated  form,  is  caused  by  visual 


208  HETEROPHORIA. 

errors;  but  it  cannot  be  asserted  that  all  choreas  are 
caused  by  ocular  defects.  It  is  safe  and  proper  to  say 
that  every  child  suffering-  with  chorea  should  be  exam- 
ined by  an  ophthalmic  surgeon  with  the  view  of  having 
any  existing-  ocular  error  adjusted.  It  is  generally  con- 
sidered that,  whatever  may  be  the  cause,  chorea  is  a  re- 
flex neurosis,  and  that  finding-  and  removing  the  cause 
brings  a  speedy  cure.  Medical  treatment,  without  ref- 
erence to  cause,  is  at  best  slow. 

EPILEPSY.  —  There  can  be  no  longer  any  room  for 
doubt  that,  in  many  cases,  epilepsy,  whether  in  the  se- 
vere or  in  the  light  form,  is  often  reflex  in  origin.  If 
wax  impacted  in  the  ear  can  be  the  cause  of  epilepsy,  is 
it  unreasonable  to  suppose  that  hyperopia  may  cause 
this  motor-psychic  disturbance?  But  it  is  no  longer  a 
matter  of  supposition;  for,  beyond  all  question,  man}7 
cases  of  epilepsy  have  been  cured  by  the  convex  lenses 
that  corrected  the  focal  error.  If  a  phimosis  can  excite 
epileptic  seizures,  is  it  any  wonder  that  the  excessive 
tension  of  muscles,  in  cases  of  heterophoria,  may  now  and 
then  be  the  cause  of  these  attacks?  In  fact,  scores  of 
epileptics  have  been  cured  by  operations  for  the  estab- 
lishment of  normal  equilibrium  between  the  ocular  mus- 
cles. Hundreds  of  other  cases  would  have  been  cured, 
before  now,  by  partial  tenotomies  and  advancements,  if 
the  principles  underlying  heterophoria  had  been  properly 


HETEROPHORIA.  209 

understood.  The  proportion  of  cases  of  epilepsy  caused 
by  heterophoria  may  not  be  large  —  no  one  knows— but 
every  case  of  epilepsy  should  be  subjected  to  a  most 
careful  examination  of  the  visual  apparatus,  by  a  compe- 
tent investigator;  and  all  focal  errors  found  should  be 
corrected  and  muscle  imbalance  should  not  be  ig-nored. 

o 

That  Stevens,  Ranney,  and  others  have  spoken  their 
convictions,  based  on  observation  and  practical  experi- 
ence, on  this  subject,  the  author  believes.  He  himself 
has  had  and  has  cured  some  cases,  while  failing  on  oth- 
ers. In  the  light  of  no  distant  future,  the  statements 
that  have  been  made  by  Stevens  and  Ranney  will  not 
appear  to  be  so  extravagant  as  some  now  judge  them. 
Of  all  the  apparently  extravagant  statements,  this  one 
is  taken  from  "Ranney  on  Nervous  Diseases,"  page  481: 
"One  of  the  most  remarkable  cases  that  ever  came  un- 
der my  observation  was  that  of  a  combination  of  chorea, 
epilepsy,  and  idiocy,  in  a  girl  about  eleven  years  of  age, 
who  completely  recovered  her  health,  strength,  and  men- 
tal faculties,  when  a  refractive  error  in  her  eyes  was 
corrected  by  glasses  and  a  serious  combination  of  muscu- 
lar defects  in  the  orbit  was  adjusted  by  tenotomy.  This 
case  was  one  that  I  saw  some  three  years  ago,  in  con- 
nection with  the  practice  of  Dr.  Stevens.  At  the  first 
examinition,  the  child  could  not  walk  without  being  sup- 
ported on  both  sides,  drooled  constantly,  talked  unintel- 


210  HETEROPHORIA. 

ligibly,  answered  questions  with  apparently  little  con- 
ception of  their  import,  could  hardly  sit  unsupported  in 
a  chair  on  account  of  chorea,  had  epileptic  seizures  re- 
peatedly during  the  day  and  night,  and  presented  a  piti- 
able and  apparently  hopeless  aspect.  I  saw  her  about  a 
year  after  the  operations  were  performed,  at  the  request 
of  Dr.  Stevens.  I  found  her  free  from  chorea  and  epi- 
lepsy, able  to  run  and  skip  a  rope  unaided,  rosy  cheeked, 
and  in  full  possession  of  her  mental  faculties."  Who 
can  wonder  that  Ranney,  having  observed  this  remarka- 
ble case,  has  become  a  firm  believer  in  the  reflex  charac- 
ter of  functional  neurotic  troubles? 

It  is  not  remarkable  that  the  refractive  error  was  de- 
tected and  measured  in  this  case,  but  it  must  have  been 
exceedingly  difficult  to  arrive  at  a  correct  understanding 
of  the  complicating  heterophoria.  The  phenomenal  re- 
sults that  followed  but  emphasize  the  importance  of  the 
early  removal  of  the  cause,  before  molecular  changes  in 
both  the  motor  and  psychic  areas  of  the  brain  shall  have 
become  unalterably  fixed. 

That  epilepsy  should  be  caused  by  abnormal  tension 
of  the  delicate  ocular  muscles  is  certainly  no  more  won- 
derful than  were  the  results  of  some  experiments  made 
by  Drs.  Dercum  and  Parker,  of  the  University  of  Penn- 
sylvania, as  published  in  the  Journal  of  Nervous  and 
Mental  Diseases,  in  1884.  Some  of  the  subjects  of  ex- 


HETEROPHORIA.  21 1 

perimentation  were  placed  by  a  table,  which  they  bare- 
ly touched  with  the  tips  of  the  fingers  of  one  or  both 
hands.  "The  fingers  were  not  allowed  to  rest  on  the 
table,  but  were  maintained,  by  constant  muscular  effort, 
barely  in  contact  with  it."  Some  of  these  subjects,  in 
from  a  few  minutes  to  an  hour,  first  became  tremulous 
and  then  violently  convulsed,  falling  to  the  ground. 
The  oftener  the  experiments  were  repeated  on  the  sus- 
ceptible subjects,  the  more  easily  were  the  convulsions 
induced.  Abnormal  muscular  tension,  in  persons  with 
unstable  nerve-centers,  caused  these  convulsions,  which 
must  have  been  very  much  like  epileptic  attacks.  Those 
experimented  on  who  had  stable  nerve-centers  did  not 
show  violent  symptoms,  but,  judging  from  that  part  of 
the  report  published  by  Ranney,  page  463,  lighter  symp- 
toms must  have  shown  themselves,  even  in  these  cases. 
Other  experiments  showed  that  severe,  long-continued 
thought,  fixed  on  one  thing,  excited  direct  trouble  in  the 
psychic  centers,  and,  sympathetically,  disturbed  the  mo- 
tor centers,  resulting  in  convulsions. 

If  the  result  of  the  experiments  made  by  Dercum  and 
Parker  had  been  more  generally  known,  there  would  be 
fewer  to  doubt  that  severe  functional  neuroses  may  be 
caused  by  abnormal  muscle  tension  in  cases  of  hetero- 
phoria  and  errors  of  refraction.  No  other  muscles  of 
the  body  have  such  a  wonderful  nervous  endowment  as 


212  HETEROPHORIA. 

the  muscles  (extrinsic  and  intrinsic)  of  the  eye.  Each 
of  the  twelve  external  muscles  and  each  of  the  four  mus- 
cles inside  the  two  eyes  has  its  individual  nerve-center, 
and,  besides  these,  there  must  be  at  least  nine  or  ten  con- 
jugate nerve-centers.  Only  the  eye  muscles  must  work 
with  mathematical  precision  so  as  to  have  sharp  images 
and  binocular  single  vision.  Any  necessity  for  overaction 
— abnormal  tension — on  the  part  of  any  ocular  muscle 
should  be  counteracted,  if  the  delicate  nervous  system 
is  to  be  freed  from  a  prolific  source  of  disturbance  that 
may  be  either  psychic,  motor,  sensory,  or  visceral. 

The  emphasis  given  above  is  not  intended  to  impress 
the  reader  with  the  idea  that  the  orbit  is  Pandora's  box, 
out  of  which  come  all  functional  ailments.  Undue  exci- 
tation of  the  brain-center  controlling  any  organ  of  the 
body  can  reflexively  disturb  other  centers  near  by  and 
remote — centers  psychic,  centers  motor,  centers  sensory, 
centers  controlling  the  viscera.  It  would  be  well  for 
humanity,  if  all  other  organs  and  parts  of  the  body 
could  be  so  thoroughly  and  scientifically  investigated  as 
can  the  eyes. 

CATALEPSY. — If  clonic  muscular  contractions,  asso- 
ciated with  unconsciousness,  can  be  caused  by  errors  of 
refraction  and  heterophoria,  the  same  errors  may  cause 
tonic  muscular  contractions — rigidity — with  mental  ob- 
livion. The  cause  should  be  sought  and,  when  found, 


HETEROPHORIA.  213 

removed.  Occasionally  excessive  tension  of  the  ocular 
muscles  is  causative  of  catalepsy. 

HYSTERIA. — This  disease  is  one  of  the  terrible  func- 
tional neuroses,  and,  like  the  others  already  considered, 
may  depend  on  focal  errors  and  imbalance  of  the  ocular 
muscles.  The  character  of  the  hysteria  in  a  given  case 
does  not  point  to  any  definite  cause.  Whether  the  man- 
ifestations are  sensory,  motor,  psychic,  visceral,  or  vaso- 
motor,  a  cure  can  be  effected,  if  the  cause  can  be  found; 
hence  the  importance  of  a  most  thorough  investigation 
of  these  unfortunates.  In  these  cases  no  investigation 
is  complete  that  leaves  out  the  visual  apparatus.  Er- 
rors of  focus  should  be  corrected,  imbalanced  muscles 
sh'ould  be  adjusted,  with  the  fair  prospect  that  at  least 
some  will  be  cured. 

NEURASTHENIA. — This  condition  of  weakness  of  the 
neuron  elements  is  the  very  opposite  of  those  just  con- 
sidered, and  yet  it  may  have  the  same  cause.  If  errors 
of  refraction  and  heterophoric  conditions  do  not  cause 
neurasthenia  in  certain  cases,  it  must  be  conceded  that 
they  can  perpetuate  it  in  all  cases.  The  results  of  the 
correction  of  errors  of  refraction,  and  the  regulation  of 
the  tension  of  the  recti  muscles  by  tenotomies  and  short- 
enings or  advancements,  have  been  so  marvelous  as  to 
justify  the  declaration  that  every  subject  of  neuras- 
thenia should  have  the  visual  apparatus  investigated. 


214  HETEROPHORIA. 

The  correction  of  any  existing-  errors,  to  say  the  least, 
would  tend  to  hasten  a  cure,  whatever  may  have  been 
the  chief  cause.  Many  cases  have  been  speedily  cured  by 
these  means  alone,  in  which  internal  medication,  electric- 
ity, and  rest  had  been  tried  in  vain.  In  any  case  in  which 
but  little  nerve  force  is  generated,  the  undue  expendi- 
ture of  that  little  should  be  prevented,  thus  giving  med- 
icine, food,  and  rest  a  better  chance  to  have  full  regen- 
erating power  restored  to  the  weak  brain  cells.  In  no 
case  should  the  correction  of  visual  errors  be  wholly  re- 
lied on,  but  other  organs  and  parts  of  the  body  should 
be  investigated,  and  all  local  diseases  found  should  be 
treated — such  as  those  of  the  stomach,  the  rectum,  the 
bladder,  the  ovaries,  and  the  womb;  for  these  may  have 
been  the  chief  cause  of  the  prostration,  the  visual  errors 
having  served  only  to  aggravate  and  perpetuate  the  neu- 
rasthenia. 

Through  the  nervous  system,  errors  of  refraction 
and  heterophoria  may  cause  functional  derangement  of 
the  thoracic,  abdominal,  and  pelvic  viscera.  Indiges- 
tion, torpidity  of  the  liver,  and  constipation  have  dis- 
appeared, in  some  cases,  as  a  result  of  the  correction 
of  visual  errors.  A  case  of  stammering  was  unexpect- 
edly cured  by  the  wearing  of  prisms  prescribed,  by  a 
Denver  oculist,  for  an  exophoria.  The  Doctor  was  so 
astonished  at  the  result  that  he  decided  to  remove  the 


KETEROPHORIA.  21 5 

prisms,  so  that  he  migLL  determine  whether  the  cure 
was  a  coincidence  or  a  consequence,  impost  hoc  or  a  prop- 
ter  hoc.  The  stammering-  retu.  -  A,  and  was  again  re- 
lieved by  the  wearing-  of  the  prisms.  Disturbed  respira- 
tion and  an  irritable  heart  have  been  quieted  by  lenses 
and  by  operations  on  the  eye  muscles.  Dr.  Hale,  of  Nash- 
ville, once  had  a  little  patient  suffering  from  a  refractive 
error,  whose  bladder  was  so  irritable  that  micturition  in 
sleep  was  almost  a  nightly  occurrence;  but  at  the  time 
of  the  examination  of  the  eyes  nothing  was  told  the  Doc- 
tor about  the  irritable  bladder.  Later  the  parents  re- 
ported that  the  glasses  had  done  more  than  was  contem- 
plated, in  that  the  irritability  of  the  bladder  had  van- 
ished. The  Doctor's  astonishment  was  great.  He  de- 
cided to  settle  the  question  of  relationship  between  the 
wearing  of  the  glasses  and  the  disappearance  of  the 
irritability  of  the  bladder,  by  withholding  the  glasses. 
Almost  immediately  the  bladder  trouble  returned,  to  dis- 
appear again,  and  permanently,  when  the  spectacles  were 
restored  to  the  child. 

It  has  been  a  matter  of  common  observation  that  dis- 
menorrhoea  in  girls  and  young  women  has  been  wholly  or 
in  part  relieved  by  a  correction  of  errors  of  the  visual 
apparatus.  These  things  are  marvelous  and  can  be  ex- 
plained only  by  assuming  that  these  remote  organs  have 
sympathized  with  the  eyes  in  their  efforts  to  correct 


216  HETEROPHORIA. 

errors  of  adjustment  and  errors  of  focus.  To  claim  that 
all  cases  like  those  referred  to  above  have  the  exciting- 
cause  in  the  eyes  would  be  absurd;  but  when  the  cause  is 
so  simple,  how  easy  and  rapid  the  cure!  So  far  the 
symptoms  considered  have  been  in  parts  more  or  less  re- 
mote from  the  eyes.  In  many  cases  the  only  symptoms 
of  eye-strain  are  in  the  eyes  themselves  or  in  their  ap- 
pendages. 

ASTHENOPIA. — This  is  a  weakness  of  the  eyes  that 
may  be  shown  in  a  sense  of  fatigue  associated  with  more 
or  less  pain  in  the  eyes,  tog-ether  with  an  excessive  secre- 
tion of  tears,  whenever  an  attempt  is  made  to  do  near 
work.  Letters,  while  being-  looked  at,  may  fade  away 
for  a  moment,  because  of  relaxation  of  weak  ciliary  mus- 
cles; the  pag-e  may  become  blurred  or  mixed  from  side  to 
side,  because  the  imbalance  of  the  lateral  recti  muscles 
momentarily  increases  the  angle  of  convergence,  as  in 
esophoria,  or  by  the  temporary  lessening-  of  this  ang-le, 
as  in  exophoria;  or  the  blurring-  may  be  from  top  to 
bottom,  caused  by  the  sudden  elevation  of  one  visual  axis 
above  the  other,  as  in  hyperphoria. 

The  conjunctival  vessels  often  become  cong-ested  be- 
cause of  visual  errors.  Likewise  the  lid  marg-ins  become 
eng-org-ed  with  blood,  scales  forming  among  the  roots  of 
the  lashes,  and  the  nutrition  of  the  lashes  themselves 
suffering.  In  high  degrees  of  muscle  imbalance,  objects 


HETEROPHORIA.  217 

in  the  distance  sometimes  become  double  momentarily. 
Not  only  may  the  external  structures  of  the  eyes  be- 
come congested  because  of  strain  to  overcome  errors, 
but  the  structures  within  the  eyes  also  may  become 
congested.  Functional  disturbances  without  and  with- 
in the  eye,  if  long  continued  and  much  aggravated, 
may  lead  to  organic  changes  and  even  result  in  the 
development  of  some  of  those  diseases  that  bring  blind- 
ness. 

One  of  the  most  troublesome  asthenopias  presents 
itself  when  a  patient  is  exposed  to  bright  light,  either 
natural  or  artificial,  and  is  caused  by  a  weak  sphincter 
of  the  iris,  which  must  keep  the  pupil  small  so  as  to 
protect  the  delicate  retina. 

TREATMENT  OF  HETEROPHORIA. 

The  treatment  of  heterophoria  must  be  determined  by 
the  kind  and  quantity  of  the  error.  Small  'errors  of  the 
recti  may  be  treated  by  prisms  in  positions  of  rest  for  the 
too  weak  muscles.  The  base  of  the  prism  must  always 
point  toward  the  muscle  to  be  favored.  In  esophoria  the 
base  would  be  out,  and  prisms  of  equal  strength  should 
be  placed  before  the  two  eyes.*  If  the  error  is  small 
and  the  interni  are  properly  attached,  or  even  if  they  are 
attached  in  greater  part  above  the  horizontal  plane,  in 

*  Exceptions  will  be  shown  in  the  chapter  on  Esophoria 


218  HETEROPHORIA. 

most  cases  they  can  be  comfortably  worn.  If  they  do 
not  give  comfort,  it  becomes  evident  that  the  interni  are 
attached  too  low,  and  that  their  forced  action  develops  a 
plus  cyclophoria,  which  becomes  a  source  of  discomfort. 
In  exophoria  the  prisms  should  be  of  equal  strength  be- 
fore the  two  eyes,*  and  their  bases  should  be  in.  If  the 
error  is  small  and  the  externi  are  correct!}"  attached,  the 
rest  prisms  would  certainly  bring  comfort,  at  least  for  a 
time.  If  the  externi  are  attached  too  low,  the  prisms, 
as  a  rule,  can  be  comfortably  worn;  but  if  they  are  at- 
tached too  high,  the  use  of  the  prisms  cannot  bring  com- 
fort because  of  the  plus  cyclophoria  developed. 

In  hyperphoria  the  correcting  prism,  in  nearly  all 
cases,  should  be  worn  only  in  front  of  the  hyperphoric 
eye,  the  base  being  placed  down,  for  the  reason  that  the 
action  of  the  superior  rectus  for  overcoming  the  prism 
develops  a  minus  cyclophoria,  which,  to  a  certain  extent, 
neutralizes  the  plus  cyclophoria  which  nearly  always  ex- 
ists. In  the  rare  cases  in  which  there  is  minus  cyclopho- 
ria, the  rest  prism  should  be  placed,  base  up,  before  the 
cataphoric  eye,  that  a  neutralizing  plus  cyclophoria  may 
be  caused.  Only  when  there  is  perfect  balance  of  the 
obliques  would  it  be  correct  practice  to  divide  the  pris- 
matic effect  between  the  two  eyes,  base  down  before  the 
hyperphoric  eye,  base  up  before  the  cataphoric  eye.  The 

*  Exceptions  will  be  shown  in  the  chapter  on  Esophoria. 


HETEROPHORIA.  219 

per  cent  of  cases  accepting-  kindly  the  rest  prism,  base 
down  before  the  hyperphoric  eye,  is  very  large ;  while 
only  a  very  small  per  cent  of  such  cases  would  be  im- 
proved by  placing-  the  rest  prism,  base  up,  before  the 
cataphoric  eye.  A  full  prismatic  correction  of  a  hyper- 
phoria  should  be  given  only  when  there  is  a  marked  com- 
plicating- cyclophoria. 

In  uncomplicated  cyclophoria,  the  patient  may  be  ben- 
efited by  wearing  a  weak  pair  of  cylinders,  axes  in  the 
arcs  of  distortion  for  the  stronger  muscles,  even  when 
there  is  no  astigmatism  ;  or,  if  there  is  astigmatism,  by 
displacing  the  axes  of  the  correcting  cylinders  in  the 
arcs  of  distortion  for  the  stronger  pair  of  obliques.  As 
will  be  shown  in  the  chapter  on  cyclophoria,  the  arc  of 
distortion  by  plus  cylinders  for  the  superior  oblique  of  the 
right  eye  has  its  center  always  at  45°,  and  for  the  left  eye 
it  has  it  at  135°;  while  the  center  of  the  arc  of  distortion 
by  plus  cylinders  for  the  inferior  oblique  of  the  right  eye 
is  always  at  135°,  and  for  the  left  eye  it  is  at  45°.  The 
reverse  is  true  of  minus  cylinders.  These  arcs  are  equal 
in  extent  only  when  the  astigmatism  is  vertical  or  hori- 
zontal, but  their  sum  is  always  180°.  The  extent  of  the 
displacement  of  the  axes  of  the  cylinders,  requisite  for 
the  relief  sought,  depends  on  the  quantity  of  cyclo- 
phoria and  the  strength  of  the  astigmatic  correction — a 
weak  cylinder,  more  displacement;  a  strong  cylinder, 


220  HETEROPHORIA. 

less  displacement.  If  there  is  no  complicating  hyper- 
phoria,  the  displacing"  effect  of  the  cylinders  should  be 
divided  equally  before  the  two  eyes;  but  if  there  is  a 
hyperphoria  complicating  a  plus  cyclophoria,  only  the 
cylinder  before  the  cataphoric  eye  should  be  displaced; 
while  the  reverse  would  be  true  when  a  hyperphoria 
complicates  a  minus  cyclophoria.  It  is  clear  that  the 
enforced  action  of  an  inferior  oblique  would  elevate  the 
corresponding  eye,  to  that  extent  neutralizing  or  correct- 
ing the  cataphoria;  while  the  enforced  action  of  a  supe- 
rior oblique  would  correspondingly  depress  the  eye  to 
which  it  belongs,  thus  diminishing,  if  not  correcting, 
the  hyperphoria.  The  displaced  cylinders  do  for  the 
weak  obliques  what  rest  prisms  do  for  the  weak  recti. 
In  both  instances  the  law  of  direction  is  infringed,  which, 
in  itself,  is  not  good.  For  this  reason  it  is  better  prac- 
tice to  relieve  all  forms  of  intrinsic  heterophoria  either 
by  exercise  or  by  operations.  An  objection  applies  to 
displaced  cylinders  that  does  not  apply  to  prisms:  by 
the  former  vision  is  rendered  less  acute,  while  by  the 
latter  there  is  no  such  interference. 

GYMNASTIC  EXERCISE. 

In  low  degrees  of  heterophoria,  of  whatever  kind,  de- 
velopment of  the  weaker  muscles  by  exercise  is  the  best 
practice.  The  time  necessary  for  curing  these  cases  by 


HETEROPHORIA.  221 

exercise  and  the  trouble  involved  in  carrying  it  out  reg- 
ularly and  systematically,  constitute  the  chief  objections 
to  this  method  of  treatment. 

What  the  author  wrote  in  1893  so  perfectly  harmo- 
nizes with  his  present  views  on  the  exercise  of  the  ocu- 
lar muscles  that  it  is  reproduced  in  the  few  following 
pages: 

The  development  of  the  ocular  muscles,  by  means  of 
gymnastic  exercise,  has  received  but  little  attention  from 
modern  authors.  Noyes  devotes  about  one  page  to  the 
subject;  DeSchweinitz,  less  than  one  page;  Schmidt- 
Rimpler,  three  lines,  as  follows,  "No  improvement  is  to 
be  expected,  as  a  general  thing,  from  exercise  of  the  in- 
terni;  overexertion,  that  is  apt  to  occur,  may  result,  on 
the  contrary,  in  a  serious  impairment  of  their  power;  " 
Fuchs,  not  a  line;  Berry,  not  a  line;  Meyer,  ten  lines; 
Landolt,  not  a  line;  Wells,  one  paragraph  of  ten  lines; 
Schweigger,  not  a  line;  Nettleship,  not  a  line;  Juler, 
not  one  word;  Carter,  not  a  line. 

Those  of  the  twelve  authors  above  named  who  teach 
anything  on  the  subject  teach  the  same  thing.  This 
teaching  is  illustrated  by  the  following  quotation  from 
DeSchweinitz:  "Thus,  to  exercise  the  interni  [in  exo- 
phoria]  a  prism  of  10°  is  placed,  base  out,  before  one 
eye,  and  as  soon  as  the  diplopia  produced  is  overcome, 
5°  more  are  added,  and  so  on  until  the  limit  of  adductive 


222  HETEROPHORIA. 

power  is  reached.  .  .  .  These  exercises  should  be 
repeated  every  day  for  ten  or  fifteen  minutes  at  a  time, 
until  the  patient  has  acquired  the  power  to  overcome 
readily  a  prism  of  50°."  He  recommends  the  same  char- 
acter of  exercise  for  developing1  the  externi,  beginning 
with  a  3°  prism  and  increasing"  to  8°. 

Noyes,  following-  Dyer,  who  wrote  on  this  subject  in  1865, 
says:  "He  [the  patient]  takes  a  candle  flame  or  door  knob 
at  twenty  feet  for  his  object,  and  performs  the  efforts  of 
adduction  and  abduction  by  means  of  these  prisms.  He 
begins,  say,  with  adduction,  and  at  first  holds  the  prism 
of  5°,  with  base  out,  before  one  eye;  then  substitutes  the 
10°;  then  before  the  other  eye  places  5°,  making-  a  total 
of  15°;  then,  if  practicable,  substitutes  the  other  prism  of 
10°  for  the  5°;  and  so  climbs  up  the  ladder  of  adduction 
prisms  by  such  steps  as  he  can  make.  If  the  interval  of 
5°  becomes  too  great,  he  may  take  that  of  23°."  He 
speaks  of  the  exercise  of  the  externi  after  the  same  plan, 
using  weaker  prisms  with  their  bases  in.  He  directs 
that  the  exercise  be  continued  ten  minutes  at  each  sit- 
ting, and  that  it  be  repeated  not  oftener  than  twice  a 
day,  until,  in  case  of  the  interni,  a  prism  of  42^°  can  be 
readily  overcome,  and,  in  the  case  of  the  externi,  a  prism 
of  10°.  The  prism  of  maximum  strength  having  been 
reached,  its  use  should  be  continued,  says  this  author, 
once  daily  for  a  time.  Noyes  closes  by  saying:  "A  de- 


HETEROPHORIA.  223 

cided  gain  in  comfort  and  use  of  the  eyes  may  be  ob- 
tained by  this  proceeding;  and  if  this  result  is  not  ade- 
quate, the  true  state  of  the  muscular  relations  is  brought 
to  view." 

It  is  not  necessary  to  make  further  quotations  in  order 
to  bring1  clearly  into  view  the  character  of  the  exercise. 
It  is  the  object  of  this  paper  to  show  that  the  plan  is 
unsound  in  principle,  and  must  necessarily  be  unsuccess- 
ful in  practice.  Continuous  muscular  contraction,  aug- 
mented at  short  intervals,  for  ten  minutes,  or  for  even  five 
minutes,  may  show  what  a  muscle  is  capable  of  doing  in 
an  emergency;  but  it  is  not  calculated  to  build  up  or  de- 
velop the  inherent  power  of  the  muscle. 

In  a  modified  form  Dr.  Charles  E}.  Michel,  of  St.  Louis, 
has  persistently  practiced  the  development  of  weak  in- 
ternal recti  muscles  by  means  of  prisms,  since  1877. 
The  prisms  used  by  him  have  not  been  stronger  than  4° 
nor  weaker  than  1°.  Beginning-  with  the  weaker  prism, 
he  directs  the  patient  to  exercise  frequently  (ten  to  fif- 
teen times)  during  the  day,  each  period  of  exercise  to 
last  only  four  or  five  minutes  for  the  first  few  days; 
later  they  are  to  be  worn  only  four  or  five  times  daily, 
increasing  the  time  of  exercise  by  two  to  five  minutes 
daily,  until  they  can  be  worn  comfortably  one  hour. 
When  the  patient,  looking  in  the  distance,  becomes  able 
to  wear  the  4°  prism  one  hour  without  discomfiture,  he 


224  HETEROPHORIA. 

is  directed  to  commence  reading.  At  first  he  must  read 
only  from  three  to  five  minutes  at  a  time;  but  later  he 
increases  this  time  by  two  to  five  minutes  daily,  until  he 
can  read  comfortably  one  hour,  four  times  a  day.  When- 
ever this  can  be  done,  the  patient  is  directed  to  continue 
for  several  months  the  reading-exercise  practice  for  from 
a  half  to  one  hour,  two  or  three  times  a  day.  To  suit 
individual  cases,  modifications  as  to  strength  of  prism 
and  length  of  time  and  frequency  of  exercise  must  be 
made. 

Under  Dr.  Michel's  treatment,  fjilly  60  per  cent  of  his 
patients  have  full  muscular  power  developed,  and  in  this 
way  are  enabled  to  use  their  eyes  with  comfort;  25  per 
cent  have  greater  or  less  gain  in  comfort;  while  15  per 
cent  derive  no  benefit  from  the  treatment.  As  a  prelim- 
inary step  to  the  muscle  treatment,  the  Doctor  always 
corrects  any  existing  refractive  errors,  and  has  the  pa- 
tient wear  these  lenses  behind  the  exercise  prisms. 

Dr.  Michel's  method  of  developing  ocular  muscles  is 
given  for  the  reason  that  it  differs  essentially  from  that 
set  forth  in  the  books,  and  for  the  additional  reason 
that  a  high  percentage  of  cures  results  from  his  method. 
The  Doctor's  success  has  been  due  to  the  fact  that  his 
\veak  prisms  used  made  but  little  demand  on  the  weak 
muscles,  thus  making  it  possible  for  the  continuous  con- 
traction to  be  borne  and  the  muscle  strengthened. 


HETEROPHORIA.  225 

In  contrast  with  Dr.  Michel's  practice,  the  method  of 
Dr.  George  T.  Stevens,  of  New  York,  is  here  given  in  his 
own  words:  "Adduction  may  be  greatly  improved  by 
gymnastic  exercises  of  the  interni,  by  means  of  prisms. 
In  these  exercises  the  eyes  are  required  to  unite  images 
in  overcoming  gradually-increasing  obstacles.  A  prism  of 
a  few  degrees,  perhaps  10°,  is  placed,  base  out,  before  one 
of  the  eyes,  \vhile  gazing  at  a  lighted  candle  at  twenty 
feet  distance,  when  an  effort  is  at  once  made  to  prevent 
diplopia.  As  soon  as  the  images  are  blended,  another 
prism,  of  perhaps  less  degree,  is  placed  in  the  same  man- 
ner. The  images  being  united,  a  stronger  prism  takes 
the  place  of  one  of  those  already  in  place,  or  one  is  add- 
ed to  those  already  in  position.  Thus,  little  b}r  little, 
the  eyes  are  required  to  overcome  prisms  until  the  im- 
ages can  no  longer  be  united.  Then  all  the  glasses  are 
removed  and  the  process  is  repeated;  with  each  repeti- 
tion something  may  be  gained.  The  exercise  should  not 
be  continued,  at  a  single  sitting,  more  than  five  or  six 
minutes;  and  only  a  single  sitting  daily  is  desirable.  By 
this  means  the  adducting  power  can,  in  most  cases,  be 
raised,  after  a  few  exercises,  to  the  desired  point. 

"The  effect  of  such  exercise  upon  the  eyes  is  very  of- 
ten extremely  salutary.  With  greater  freedom  of  mus- 
cular action  comes  a  sense  of  relief  from  nervous  strain, 
which  is  often  of  a  most  gratifying  character.  Such  an 


226  HETEROPHORIA. 

exercise  is  in  no  way  related  to  the  practice  sometimes 
adopted,  and  which  should  be  condemned,  of  requiring 
the  patient  to  gaze  for  a  long  time  at  a  near  object." 

The  virtue  of  Dr.  Michel's  method  lies  in  the  fact 
that,  though  he  taxes  the  muscles  for  a  long  while, 
gradually  reaching  the  maximum  of  time,  he  taxes  them 
but  slightly,  using  only  weak  prisms;  while  the  virtue 
of  Dr.  Stevens'  method  lies  in  the  fact  that,  though  he 
taxes  the  muscles  severely,  using  the  strongest  prisms 
possible,  reaching  the  maximum  strength  by  degrees,  he 
does  not  continue  the  exercise  very  long  and  does  not  re- 
peat the  sitting  again  the  same  day.  And,  too,  he  al- 
most strikes  the  right  principle  in  his  method  of  inter- 
mitting- the  exercise.  In  contrast  with  both  of  these 
methods,  and  with  the  methods  laid  down  in  the  books, 
the  method  of 

RHYTHMIC  EXERCISE 

will  now  be  given,  the  author  feeling  confident  that  it  is 
founded  on  sound  principles  and  that  it,  therefore,  can  be 
carried  out  successfully  in  practice. 

Contraction  and  relaxation,  alternating  in  short  and 
rhythmic  order,  and  continued  short  of  fatigue,  is  the 
kind  of  exercise  that  develops  a  muscle  in  any  part  of  the 
body.  It  is  the  alternate  contraction  and  relaxation  that 
develops  the  muscles  of  the  arm  of  the  blacksmith.  If 


HETEROPHORIA.  227 

the  forearm  should  be  flexed  on  the  arm  and  held  in  that 
position  ten  minutes,  no  one  would  suppose  that  the 
muscles  concerned  could  be  developed  thereby.  There 
would  be  greater  reason  for  believing-  that  such  action 
would  enfeeble  the  muscles.  This  is  precisely  the  kind 
of  contraction  effected  by  prisms  in  the  old  method  of 
exercising  the  recti  muscles.  There  can  be  no  wonder 
that  better  results  have  not  followed,  and  that  the  prac- 
tice has  been  abandoned  by  almost  all  oculists. 

It  would  be  of  little  worth  to  condemn  the  old  practice 
as  bad  without  setting  forth  a  new  line  of  practice, 
based  on  sound  principles,  and  one  that  must  be  success- 
ful, in  suitable  cases. 

While  rhythmic  contraction  and  relaxation,  regulated 
as  to  intensity  and  time,  will  develop  any  one  of  the  recti 
muscles,  as  is  developed  the  biceps  of  the  blacksmith's 
arm,  the  writer  would  not  be  understood  as  believing  that 
one  of  these  muscles  can  be  developed  out  of  a  loiv  state 
of  weakness  into  a  high  state  of  strength.  There  are 
cases  of  exophoria  that  will  remain  exophoric  still,  in 
spite  of  long-continued  rhythmic  and  graduated  exercise; 
and  these  cases,  to  be  cured  at  all,  must  be  cured  either 
by  partial  tenotomies  alone  or  by  these  supplemented 
with  rhythmic  exercise.  The  same  may  be  said  of  eso- 
phoria  and  of  hyperphoria.  Only  low  degrees  (not  more 
than  6°)  of  lateral  heterophoria  can  be  converted,  by 


228  HETEROPHORIA. 

rhythmic  exercise  alone,  into  orthophoria;  the  higher 
degrees  can  be  corrected  by  partial  tenotomies,  shorten- 
ing's, and  exercise  combined.  While,  in  suitable  cases, 
the  aim  of  partial  tenotomies  and  shortenings  should  be 
to  approach  orthophoria,  yet  the  greatest  care  should 
be  exercised  not  to  go  beyond  the  "balance"  line.  The 
safest  thing  is  to  leave,  for  correction  by  exercise,  some 
of  the  original  condition. 

Any  one  of  the  recti  and  either  of  the  obliques  weaker 
than  its  opposing  muscle,  the  difference  in  correspond- 
ing strength  not  being  too  great,  may  be  developed  by 
rhythmic  exercise  into  a  state  that  will  enable  it  to  work 
harmoniously  with  its  fellow. 

EXERCISE  FOR  EXOPHORIA. 

Exophoria  may  be  taken  first  for  study.  The  quanti- 
ty should  not  be  more  than  6°.  The  internal  recti  are 
the  muscles  wanting  in  strength.  There  are  two  plans 
of  exercise,  rhythmic  in  their  nature,  by  either  one  of 
which,  or  by  both  combined,  these  muscles  can  be  per- 
ceptibly strengthened: 

(1)  The  wax  taper  method; 

(2)  The  method  by  prisms,  bases  out. 

The  exercise  with  the  taper  (small  wax  candle)  must 
be  conducted  as  follows:  The  patient  is  directed  to  light 
the  taper  and  hold  it  at  arm's  length  from,  and  on  a 


HETEROPHORIA.  229 

plane  with,  the  eyes,  immediately  in  front  of  the  face. 
Fixing-  his  vision  on  the  flame,  he  continues  to  look  at  it 
while  he  brings  it  slowly  to  within  seven  inches  of  his 
eyes,  holding-  it  there  about  two  seconds.  He  then  closes 
his  eyes  for  a  moment  (at  the  same  time  moving-  the 
candle  to  one  side)  and,  on  opening  them,  fixes  his  vision 
on  some  distant  object.  The  same  procedure  is  gone 
through  with  a  second  time,  and  so  on  for  five  to  fifteen 
times  at  one  sitting.  The  sittings  may  be  repeated  one 
or  more  times  daily  for  weeks  or  months.  The  best  time 
for  this  exercise  is  early  in  the  morning,  while  the  mus- 
cles are  fresh  from  sleep.  In  many  cases  the  morning 
sitting  will  be  sufficient  for  the  day.  This  is  especially 
so  if  the  exophoria  is  low  in  degree.  Reading  or  other 
near  work  should  not  be  done  within  the  hour  after  the 
exercise  is  taken. 

In  this  taper  exercise  no  one  can  doubt  that  the  guid- 
ing- sensation  compels  the  internal  recti  to  contract,  in 
obedience  to  the  law  of  corresponding  retinal  points,  as 
the  light  advances,  the  maximum  of  contraction  being 
reached  when  the  taper  is  seven  inches  from  the  eyes. 
On  closing  the  eyes  partial  relaxation  of  the  interni  oc- 
curs (keeping  the  eyes  closed  long  enough,  the  relaxa- 
tion would  become  complete).  The  moment  the  eyes  are 
opened  and  the  vision  is  fixed  on  a  distant  object,  in 
quick  response  to  the  guiding  sensation,  the  relaxation 


230  HETEROPHORIA. 

becomes  complete.  Thus  is  brought  about  contraction 
and  relaxation,  which  should  be  discontinued  short  of 
fatigue.  That  this  rhythmic  exercise,  properly  regulat- 
ed as  to  frequency  and  force,  will  develop  the  internal 
recti,  is  susceptible  of  demonstration  on  the  part  of  any 
one  who  wishes  to  know  the  truth. 

The  second  method  for  developing  the  interni  is  by 
means  of  prisms,  bases  out.  The  prisms  to  be  used  may 
be  from  1°  to  8°,  and  one  should  be  placed  before  each  eye. 
The  treatment  should  be  commenced  with  the  weaker 
prisms,  and  as  development  of  the  muscles  advances, 
the  stronger  should  be  brought  into  use.  The  object 
looked  at  should  be  a  candle,  lamp,  or  gas  jet,  fifteen 
to  twenty  feet  distant.  With  the  prisms  before  the  eyes, 
the  image  in  each  eye  is  displaced  out,  when  the  guiding- 
sensation  calls  quickly  into  action  the  interni  for  fusing 
them.  After  three  seconds  the  interni  must  be  allowed 
to  relax  for  the  same  length  of  time  (three  seconds), 
which  is  readily  effected  by  lifting  the  prisms  up  and  al- 
lowing the  light  to  enter  the  eyes  uninfluenced.  The 
guiding  sensation  at  once  causes  the  relaxation  to  take 
place,  so  that  the  yellow  spots  may  receive  the  images. 
At  the  end  of  three  seconds  the  prisms  are  again  dropped 
before  the  eyes,  when  the  interni  again  contract.  Then 
a  second  time  the  relaxation  is  effected  by  lifting  the 
prisms;  and  so  on  throughout  every  sitting,  which  should 


HETEROPHORIA.  231 

last  from  two  to  ten  minutes,  but  should  always  be  dis- 
continued short  of  fatigue.  The  sittings  should  be  re- 
peated two  or  more  times  a  day.  While  it  will  take 
weeks,  if  not  months,  to  establish  orthophoria,  neverthe- 
less this  end  can  be  attained,  in  suitable  cases,  by  this 
method.  It  may  be  better  in  most  cases  to  resort  to  the 
two  methods  of  development,  the  taper  and  the  prisms, 
each  day,  but  not  at  the  same  sitting. 

In  resorting  to  the  prism  exercise,  it  would  be  more  con- 
venient to  close  the  eyes,  for  the  purpose  of  getting  re- 
laxation, than  to  lift  the  prisms;  but  when  the  eyes  are 
closed  the  relaxation  is  slow  to  take  place,  and  is  rarely 
complete  at  the  end  of  sixty  seconds;  whereas,  when  the 
prisms  are  raised,  the  guiding  sensation  effects  at  once' 
complete  relaxation,  which  continues  till  the  prisms  are 
again  placed  before  the  eyes.  The  rhythmic  nature  of 
the  exercise  is  more  perfect  in  the  latter  than  in  the  for- 
mer, and  results  are  better  necessarily. 

The  method  of  exercise  of  the  interni  by  means  of 
strong  prisms,  introduced  by  Dr.  Deady,  of  New  York, 
and  later  reintroduced  and  earnestly  advocated  by  Gould, 
may  have  its  merits,  but  certainly  not  in  the  line  of  mus- 
cle building.  The  good  resulting  from  this  method  must 
come  through  excitation  of  the  converging  center,  that 
of  the  third  conjugate  innervation.  An  overdraft  on  a 
nerve-center  may  be  endured  for  a  time,  but  should  be 


232  HETEROPHORIA. 

avoided,  if  possible.  Ultimately  exhaustion  would  be 
expected  to  follow.  At  any  rate,  it  would  seem  to  be  far 
better  to  change  the  condition  of  the  muscles  so  that  the 
normal  nerve  impulse  would  make  them  do  their  work 
properly.  That  a  muscle  can  be  made  stronger  by  light 
rhythmic  exercise,  never  carried  to  the  point  of  fatigue, 
does  not  admit  of  a  doubt.  The  muscular  Sandow,  capa- 
ble of  lifting  many  hundred  pounds,  developed  his  mus- 
cles by  rhythmic  exercise  with  three-pound  dumb- 
bells. 

Without  endorsing  the  use  of  strong  prisms,  in  exo- 
phoria,  the  method  must  here  be  given.  The  exer- 
cise begins  at  a  point  twenty  inches  distant  from  a 
lighted  candle  or  gas  jet,  by  placing  before  the  eyes  the 
strongest  prisms,  bases  out,  that  can  possibly  be  over- 
come. At  once  the  light  is  carried  from  the  patient,  or 
the  patient  recedes  from  the  light,  until  a  distance  of 
twenty  feet  intervenes.  The  prisms  are  then  raised, 
when,  of  course,  relaxation  occurs.  When  again  within 
twenty  inches  of  the  light,  the  prisms  are  lowered,  and 
recession  follows  as  before.  Thus  the  exercise  is  con- 
tinued from  three  to  five  minutes,  the  powerful  contrac- 
'  tions  and  full  relaxations  following  each  other  every 
seven  seconds.  The  periods  of  exercise  are  to  be  repeat- 
ed several  times  a  day.  Very  strong  claims  have  been 
made  for  this  method,  and  there  may  be  more  in  it  than 


HETEROPHORIA.  233 

would  appear  from  reasoning-  about  it;  but  its  most  ar- 
dent advocates  confine  its  use  to  the  treatment  of  ex- 
ophoria. 

ESOPHORIA. 

In  this  condition  the  muscles  to  be  built  up  are  the  ex- 
ternal recti.  There  is  but  one  method  for  doing  this, 
and  that  is  by  means  of  prisms.  These  should  be  from 
2°  to  3°,  certainly  not  more  than  4°,  and  their  bases  must 
be  placed  in.  Beginning  with  the  weaker  prisms,  the 
patient  should  look  at  the  candle  twenty  feet  distant  for 
three  seconds,  during  which  time  the  guiding  sensation 
has  caused  the  externi  to  undergo  contraction;  and  then 
the  prisms  should  be  held  up  for  three  seconds  to  allow 
relaxation  to  take  place.  These  steps  should  be  thus 
regularly  repeated  throughout  each  sitting  of  two  to  ten 
minutes,  the  sittings  themselves  being  repeated  two  or 
more  times  daily,  as  in  the  treatment  of  exophoria.  In 
suitable  cases  orthophoria  can  be  brought  about. 

HYPERPHORIA. 

Hyperphoria  and  cataphoria,  like  esophoria,  are  sus- 
ceptible to  exercise  only  by  means  of  prisms.  Given  a 
case  of  left  hyperphoria  (right  cataphoria)  of  not  more 
than  1^°,  there  is  a  possibility  of  developing  vertical  or- 
thophoria by  means  of  rhythmic  exercise.  The  muscle 
on  the  left  side  to  be  developed  is  the  inferior  rectus, 


234  HETEROPHORIA. 

and  that  on  the  right  side  is  the  superior  rectus.  The 
prisms  used  should  vary  from  ^°  to  2°;  most  cases  will 
not  require  a  stronger  than  a  1°  prism.  The  base  of  the 
left  prism  must  be  up;  that  of  the  right  prism,  down. 
As  in  exophoria  and  esophoria,  the  patient  should  exer- 
cise from  two  to  ten  minutes  at  a  time,  and  two  or  more 
times  a  day.  The  object  looked  at  should  be  twenty 
feet  distant,  and  it  should  be  seen  through  the  prisms 
three  seconds,  then  without  the  prisms  three  seconds, 
and  so  on  throughout  each  sitting.  Thus  contraction 
and  relaxation  of  the  weak  left  inferior  rectus  and  weak 
•'right  superior  rectus  are  effected  in  rh}rthmic  order.  If 
.  the  hyperphoria  is  on  the  right  side  (left  cataphoria), 
the  base  of  the  right  prism  must  be  up  and  that  of  the 
left  prism  must  be  down,  when  exercising.  In  every 
form  of  heterophoria  the  apex  of  the  prism  must  point 
in  the  direction  of  the  muscle  to  be  developed  by  it. 

Occasionally  cases  present  themselves  in  which  there 
is  a  general  weakness  of  the  recti  muscles,  and  especial- 
ly of  the  external  and  internal  recti,  unaccompanied  by 
general  physical  weakness.  Such  cases  generally  mani- 
fest esophoria  for  distance  and  exophoria  in  the  near, 
neither  muscle  being  able  to  overcome  a  prism  of  any- 
thing like  the  usual  strength.  To  operate  on  such  a 
case  would  be  improper,  since  relief  of  the  exophoria  in 
the  near  would  be  attended  by  a  corresponding  increase 


HETEROPHORIA.  235 

of  the  esophoria  for  distance,  and  rice  rcrsa.  In  such 
cases  the  intern!  should  be  brought  under  the  influence 
of  the  rhythmic  exercise,  as  already  set  forth  in  the 
study  of  exophoria,  at  one  time  of  the  day;  and,  at  some 
other  time  of  the  day,  like  attention  should  be  paid  to 
the  external  recti,  as  in  simple  esophoria.  In  these 
cases  strychnia  and  electricity  could  be  used  with  some 
promise  of  aiding  the  exercise  treatment.  Such  patients 
should  be  allowed  to  undertake  but  little  near  work,  un- 
til the  exercise  treatment  by  means  of  prisms  has  be- 
come well  advanced.  In  these  cases  the  wax-taper  treat- 
ment of  the  internal  recti  is  not  applicable  until  late  in 
the  course.  These  cases  are  far  more  stubborn  than 
cases  of  simple  exophoria  or  simple  esophoria;  and  yet 
great  advantage  can  be  derived  from  the  rhythmic  exer- 
cise by  means  of  weak  prisms,  aided  by  strychnia  and 
electricity. 

For  cases  showing  esophoria  in  the  distant  test  and  | 
exophoria  in  the  near,  adduction  and  abduction  both  be- 
ing low,  wall-to-wall  exercise,  probably,  can  accomplish 
more,  in  a  shorter  time,  than  the  prism  exercise  referred 
to  above.  To  perform  this  task  the  patient  must  stand 
against  one  wall  of  his  room,  equally  distant  from  the 
walls  on  the  right  and  left;  previously  there  must  have 
been  pinned  to  the  right  and  left  walls  two  pieces  of 
white  paper,  each  at  an  angle  of  35°  from  the  patient 


236  HETEROPHORIA. 

when  in  position  for  exercising,  and  as  high  from  the 
floor  as  are  his  eyes.  With  his  head  in  the  primary  po- 
sition and  his  face  directed  toward  the  middle  line  of 
the  opposite  wall,  he  must  stiffen  his  neck  while  looking 
first  at  one  piece  of  paper  and  then  at  the  other,  chang- 
ing from  the  one  to  the  other  with  the  regularity  and  in- 
terval of  the  tick  of  an  old-time  clock.  This  should  be 
discontinued  short  of  fatigue,  and  need  not  be  prolonged 
over  five  minutes.  It  may  be  done  once  or  twice  a  day. 
If  exophoria  in  the  near  is  5°  or  more,  the  candle  exercise 
may  be  resorted  to  once  a  day  and  the  wall-to-wall  ex- 
ercise once  a  day.  Since  this  method  of  exercise  costs 
nothing,  and  the  patient  is  more  impressed  with  the  fact 
that  he  is  doing  something,  in  many  cases  it  is  better  to 
prescribe  it  than  the  prism  method. 

As  in  lateral,  so  in  vertical,  heterophoria,  the  imbal- 
ance may  be  associated  with  subnormal  superduction 
and  sub-duction.  In  such  a  case  the  prism  exercise 
should  be  resorted  to  once  a  day  for  curing  the  imbal- 
ance, and  the  ceiling-to-floor  exercise  once  a  day,  always 
short  of  fatigue,  but  never  longer  than  five  minutes. 
To  do  the  ceiling-to-floor  exercise,  the  patient  must 
place  himself  as  for  the  wall-to-wall  exercise.  A  piece 
of  paper,  a  spool  of  thread,  or  a  pocketknife  should  be 
placed  on  the  floor  as  far  in  front  of  the  patient  as  he  is 
tall.  Fixing  his  head  in  the  primary  position,  he  is  di- 


HETEROPHORIA.  237 

rected  to  look  first  at  the  object  on  the  floor,  and  then  up 
at  the  junction  of  ceiling  and  wall,  changing-  from  the  one 
point  of  view  to  the  other,  as  in  the  wall-to-wall  exercise. 

Occasionally  there  will  be  both  a  lateral  and  a  vertical 
imbalance  with  the  duction  power  of  every  rectus  below 
normal.  In  such  a  case  the  candle  exercise  for  exopho- 
ria  in  the  near,  the  prism  exercise  for  the  vertical  im- 
balance, and  the  conjoined  wall-to-wall  and  ceiling-to- 
floor  exercise  should  be  resorted  to.  In  combining  the 
wall-to-wall  and  ceiling-to-floor  exercise,  it  is  best  done 
by  looking,  from  four  to  six  times,  from  wall  to  wall,  and 
then,  from  four  to  six  times,  from  ceiling  to  floor,  con- 
tinuing thus  to  alternate  for  not  longer  than  ten  min- 
utes, but  always  short  of  fatigue. 

In  cases  in  which  the  recti  muscles  are  weak,  because 
of  a  low  state  of  general  health,  no  treatment  should  be 
thought  of  except  that  intended  for  the  well-being  of 
the  whole  system.  Use  of  the  eyes  in  near  work  should 
be  prohibited  until  recovery  of  the  general  health  has 
occurred. 

CYCLOPHORIA. 

The  treatment  of  insufficiency  of  the  oblique  muscles* 
is  by  means  of  cylindrical  lenses  (preferably  convex),  so 
placed  as  to  lead  the  guiding  sensation  to  demand  con- 

See  Ophthalmic  Record,  Vol.  II.,  No.  I. 


238  HETEROPHORIA. 

traction  on  the  part  of  the  weak  muscles.  The  +1.50  D. 
cylinder  is  the  most  useful,  but  a  weaker  one  may  be 
used  at  the  beginning.  One  should  be  placed  before 
each  eye;  and  if  the  weak  muscles  are  the  superior  ob- 
liques, their  axes  must  be  placed  in  the  lower  temporal 
quadrant,  at  first  15°  from  the  vertical,  when,  because  of 
slight  retinal  displacement  of  the  object  looked  at,  only 
a  slight  demand  is  made  on  the  muscles,  which  should 
be  kept  up,  in  an  intermitting  way,  for  five  minutes; 
then  the  axes  should  be  revolved  to  30°  from  the  verti- 
cal, when,  because  of  a  greater  displacement  of  the  im- 
ages, a  greater  demand  for  contraction  is  made  on  the 
part  of  the  weak  obliques,  which  should  be  kept  up 
intermittingly  for  three  minutes;  now,  lasth',  the  axes 
of  the  cylinders  are  revolved  to  45°  from  the  vertical, 
when  the  maximum  displacement  of  the  images  occurs, 
and  hence  the  maximum  demand  is  made  on  the  muscles, 
which  should  be  continued  intermittingly  for  two  minutes 
only.  As  in  the  exercise  of  the  recti  by  means  of  prisms, 
the  best  way  to  get  contraction  and  relaxation  alter- 
nately and  in  rhythmic  order,  is  to  lower  and  raise  the 
frames  containing  the  prisms  every  three  seconds,  so, 
to  get  rhythmic  contraction  and  relaxation  of  the  ob- 
liques under  exercise,  it  is  best  to  raise  and  lower  the 
frames  containing  the  cylinders  every  three  seconds 
throughout  the  sitting.  It  is  unfortunate  for  the  con- 


HETEROPHORIA.  239 

venience  of  the  patient  that  the  relaxation  of  ocular 
muscles  does  not  quickly  follow  the  closing*  of  the  eyes, 
since  it  would  be  much  easier  to  open  and  close  the 
eyes  every  three  seconds  than  to  lower  and  raise  the 
frames  at  the  same  interval.  The  oblique  muscles  re- 
lax much  more  readily  than  the  recti,  on  closing1  the 
eyes,  but  even  these  do  not  completely  relax  in  the  short 
time  of  five  seconds. 

In  most  cases  of  insufficiency  of  the  obliques,  exercis- 
ing" by  means  of  cylinders  once  a  day  is  sufficient;  the 
best  time  for  this  exercise  is  before  breakfast.  The  ob- 
ject looked  at  should  be  a  horizontal  black  line  on  a  white 
background  or  a  white  line  on  a  black  background,  at  a 
distance  of  ten  feet.  The  cylinders  should  be  properly 
centered. 

What  prisms  are  to  the  recti,  cylinders  are  to  the  ob- 
liques. In  either  case  the  lenses  correcting-  refractive 
errors  should  be  worn  during-  the  exercise,  in  order  that 
the  best  results  may  follow.  The  only  exception  to  this 
rule  is  the  wax-taper  exercise  of  the  internal  recti,  when 
no  lenses  should  be  worn. 

OPERATIVE  TREATMENT. 

The  heterophorias  not  curable  by  correction  of  errors 
of  refraction,  by  prisms  in  position  of  rest,  or  by  rhyth- 
mic exercise,  should  be  subjected  to  operative  procedure. 


240  HETEROPHORIA. 

Such  cases  are  not  infrequent,  and  the  relief  from  opera- 
tions skillfully  done  is  by  no  means  uncertain.  There  is 
no  department  of  surgery  that  requires  more  care  in  the 
making-  of  the  diagnosis.  The  condition  of  every  extrin- 
sic ocular  muscle  must  be  determined  before  any  one 
muscle  is  to  be  operated  upon.  There  are  but  two  ob- 
jects in  view  in  muscle  operations:  the  one  is  altering 
the  tension  of  a  muscle,  the  other  is  chang-ing-  its  plane 
of  action.  The  tension  of  a  muscle  is  to  be  altered  either 
by  a  central  partial  tenotomy,  as  when  operating  on  the 
too  strong  muscle;  by  shortening  the  muscle  in  the  line 
of  its  original  plane,  or  by  advancing  it  straight  for- 
ward, as  when  operating  on  the  too  weak  muscle.  In 
making  either  one  of  these  operations,  the  existence  of  a 
cyclophoria  must  be  first  excluded.  When  there  is  a  cy- 
clophoria  complicating  any  one  of  the  other  heteropho- 
rias,  the  operation  on  a  rectus  muscle  should  alter  the 
tension  of  the  muscle  and,  at  the  same  time,  change  the 
plane  of  its  action.  In  such  a  case  a  partial  tenotomy 
should  not  be  central  only,  but  should  include  those  pe- 
ripheral fibers,  a  division  of  which  would  be  corrective  of 
the  cyclophoria.  A  shortening  should  be  done  in  such  a 
way  as  either  to  raise  or  depress  the  plane  of  action  of 
the  muscle  as  might  be  indicated  by  the  complicating  cy- 
clophoria. In  making-  advancements,  the  new  attach- 
ment should  be  carried  either  higher  or  lower  than  the 


HETEROPHORIA.  241 

original  attachment,  as  the  character  of  the  cyclophoria 
might  determine. 

The  operation  to  simply  alter  the  tension  of  a  rectus 
muscle  with  the  view  of  lessening  its  power  is  a  central 
partial  tenotomy.  The  operator  should  always  be  care- 
ful to  leave  a  sufficient  number  of  peripheral  fibers  to 
act  as  stay  cords  to  prevent  the  cut  muscle  from  re- 
tracting- too  much.  The  strength  of  the  uncut  fibers 
in  both  directions  should  be  equal,  so  that  the  plane  of 
the  muscle  may  not  be  changed.  Both  judgment  and 
skill  must  be  exercised,  else  too  much  or  too  little  of 
the  tendon  may  be  cut.  It  is  better  to  aim  at  leaving 
some  of  the  old  error  uncorrected  than  to  transform  it 
into  the  opposite  condition.  The  conjunctiva  may,  but 
the  capsule  of  Tenon  must,  be  divided  coextensively  with 
the  division  of  the  tendon,  to  obtain  the  effect  desired. 
In  no  kind  of  heterophoria  should  a  complete  tenotomy 
ever  be  done;  but  if  by  accident  it  should  happen,  the 
tendon  should  be  stitched  to  the  sclera  directly  behind 
the  original  insertion,  and  at  that  distance  behind  de- 
termined by  a  correct  understanding  of  the  exact  char- 
acter of  the  error  for  which  the  operation  has  been  un- 
dertaken. 

If  a  complicating  cyclophoria  is  to  be  corrected  by  a 
partial  tenotomy  of  a  rectus,  not  only  must  the  tension 
of  the  muscle  be  altered  for  the  correction  of  the  main 


242  HETEROPHORIA. 

error,  but  its  plane  must  be  changed  so  as  to  correct  the 
complicating-  cyclophoria.  The  kind  of  cyclophoria  hav- 
ing- been  determined — and  it  is  nearly  always  a  plus  cy- 
clophoria— one  is  not  left  in  doubt  as  to  how  the  opera- 
tion should  be  done.  To  cure  a  sthenic  hyperphoria  and 
a  plus  cyclophoria,  the  nasal  and  central  fibers  of  the  su- 
perior rectus  of  the  hyperphoric  eye  should  be  divided, 
while  the  temporal  fibers  should  be  left  uncut  and  suffi- 
ciently strong  to  prevent  any  over-correction  of  the  hy- 
perphoria; or  the  temporal  and  central  fibers  of  the 
inferior  rectus  of  the  cataphoric  eye  should  be  divided, 
leaving  the  nasal  fibers  uncut  and  of  sufficient  strength 
to  prevent  an  over-correction  of  the  error. 

In  a  partial  tenotomy  for  a  sthenic  esophoria  compli- 
cated with  a  plus  cyclophoria,  there  being  no  hyperpho- 
ria, the  lower  and  some  of  the  central  fibers  of  both  interni 
should  be  divided,  leaving  the  upper  fibers  uncut.  In 
this  way  the  tension  of  the  muscle  is  altered,  curing, 
wholly  or  in  part,  the  esophoria,  and  the  plane  of  each 
muscle  is  elevated  so  as  to  correct  the  plus  cyclophoria. 
The  plane  of  both  interni  having  been  equally  elevated, 
there  is  of  necessity  developed  a  slight  double  hyperpho- 
ria— which,  however,  will  give  no  trouble,  being  easily 
overcome  by  a  pose  of  the  head. 

In  operating  on  a  case  of  sthenic  esophoria  compli- 
cated by  a  right  hyperphoria  and  a  plus  cyclophoria,  the 


HETEROPHORIA.  243 

first  operation  must  be  done  on  the  internus  of  the  cata- 
phoric eye,  and  should  consist  of  a  complete  division  of 
the  lower  and  central  fibers,  leaving  uncut  the  upper 
fibers  of  the  tendon.  The  threefold  effect  of  this  pro- 
cedure is  a  correction,  in  part  or  wholly,  of  the  esophoria; 
a  correction  of  thecataphoria;  and  a  cure  of  the  plus  cy- 
clophoria.  Whatever  part  of  the  esophoria  may  remain 
after  this  operation  should  be  corrected  by  a  partial  cen- 
tral tenotomy  of  the  right  internus.  Should  some  of 
the  right  hyperphoria  remain,  but  no  cyclophoria,  a  par- 
tial central  tenotomy  of  the  right  superior  rectus  should 
be  done;  but  if  there  should  remain  some  uncorrected 
plus  cyclophoria  as  well  as  right  hyperphoria,  the  inner 
and  enough  of  the  central  fibers  of  the  right  superior 
rectus  should  be  cut  to  cure  these  conditions.  These 
three  operations — sometimes  even  one  or  two  of  them— 
will  cure  a  complicated  case  of  this  character. 

If  the  esophoria  is  asthenic  and  uncomplicated,  the 
operation  of  shortening  should  be  done  on  one  or  both 
externi,  and  the  plane  of  these  muscles  should  be  the 
same  after  as  before  the  operation,  otherwise  a  hyper- 
cyclophoria  would  be  created. 

If  the  asthenic  esophoria  is  complicated  with  a  right 
hyperphoria  only,  the  externi  should  be  shortened  as 
though  no  complication  existed,  and  later  the  hyperpho- 
ria could  be  treated  by  exercise,  by  a  prism  in  position 


244  HETEROPHORIA. 

of  rest  for  the  hyperphoric  eye,  or  by  a  central  tenotomy 
of  the  superior  rectus  of  the  hyperphoric  eye.  In  such 
a  condition  no  muscle  plane  should  ever  be  changed. 
The  plane  of  a  muscle  should  never  be  changed  unless 
there  is  a  cyclophoria  to  be  corrected. 

If  the  asthenic  esophoria  should  be  complicated  with  a 
plus  cyclophoria  alone,  not  only  should  both  externi  be 
shortened,  but  the  plane  of  each  should  be  depressed  so 
as  to  cure  both  the  esophoria  and  plus  cyclophoria. 

If  the  asthenic  esophoria  is  complicated  by  a  right  hy- 
perphoria  and  a  plus  cyclophoria,  the  first  operation 
should  be  on  the  externus  of  the  hyperphoric  eye,  and 
should  be  a  shortening  so  done  as,  at  the  same  time,  to 
depress  the  plane  of  its  action.  The  triple  effect  will 
be  to  cure,  more  or  less  completely,  the  esophoria,  the 
right  hyperphoria,  and  the  plus  cyclophoria.  If  the  left 
externus  must  be  shortened  for  a  remaining  esophoria, 
whether  complicated  or  not  by  a  cataphoria  and  plus  cy- 
clophoria, one  or  both,  for  obvious  reasons  the  plane  of 
this  muscle  should  not  be  altered.  If  the  plane  were 
elevated,  it  would  lessen  the  cataphoria,  but  would  in- 
crease the  plus  cyclophoria;  if  the  plane  were  lowered, 
it  would  decrease  the  plus  cyclophoria,  but  would  in- 
crease the  cataphoria.  After  the  straight-forward  short- 
ening of  the  externus  of  the  cataphoric  eye,  whatever 
hyperphoria  alone  may  exist  should  be  treated,  if  suffi- 


HETEROPHORIA.  245 

ciently  great  in  quantity,  by  a  central  partial  tenotomy 
of  the  superior  rectus  of  the  hyperphoric  eye;  but  if  the 
remaining-  hyperphoria  should  be  complicated  with  a  re- 
maining- plus  cyclophoria,  the  inner,  and  as  much  as 
necessary  of  the  central,  fibers  of  the  superior  rectus  of 
the  hyperphoric  eye  should  be  cut. 

The  operation  for  sthenic  exophoria,  uncomplicated,  is, 
a  central  partial  tenotomy  of  one  or  both  externi,  prefer- 
ably both.  The  object  in  view  being-  only  the  alteration 
of  tension,  care  must  be  exercised  that  the  plane  of  rota- 
tion shall  not  be  chang-ed. 

When  sthenic  exophoria  is  complicated  by  a  hyper- 
phoria, the  operation  on  the  externi  must  not  be  done 
with  a  view  of  affecting-  the  hyperphoria,  hence  central 
partial  tenotomies  are  indicated.  Later  the  hyperpho- 
ria must  be  relieved  by  a  central  partial  tenotomy  of  the 
superior  rectus  of  the  hyperphoric  eye  and,  if  necessary, 
a  central  partial  tenotomy  of  the  inferior  rectus  of  the 
cataphoric  eye.  The  tension  of  these  muscles  should  be 
altered  without  a  chang-e  of  plane. 

In  sthenic  exophoria,  complicated  by  a  right  hyper- 
phoria and  a  plus  cyclophoria,  the  first  operation  should 
be  done  on  the  externus  of  the  hyperphoric  eye,  and  it 
should  consist  of  a  division  of  the  upper  and  central 
fibers,  leaving-  uncut  the  lower  fibers.  The  threefold  re- 
sult of  this  operation  will  be:  (1)  relaxing-  the  tension  of 


246  HETEROPHORIA. 

the  externus,  lessening,  if  not  curing,  the  exophoria;  (2) 
a  turning-  of  the  eye  down,  thus  counteracting-  the  hy- 
perphoria;  (3)  torting  the  eye  in,  curing  the  cyclophoria. 
If  some  of  the  exophoria  remain,  whether  still  compli- 
cated or  not  by  a  right  hyperphoria  and  a  plus  cyclopho- 
ria, the  operation  on  the  left  externus  must  be  a  central 
partial  tenotomy.  The  reason  is  clear:  a  division  of  the 
upper  and  central  fibers  would  so  change  the  muscle 
plane  as  to  increase  the  cataphoria,  although  diminish- 
ing the  cyclophoria;  while  a  cutting  of  the  lower  and 
central  fibers  would  so  change  the  plane  as  to  lessen  the 
cataphoria,  but  increase  the  plus  cyclophoria.  The  only 
safe  course  between  this  Scylla  and  Charybdis  is  a  cen- 
tral partial  tenotomy  of  the  left  externus.  These  two 
operations  having  been  done,  any  remaining  right  hyper- 
phoria, without  a  plus  cyclophoria,  should  be  relieved  by 
a  central  partial  tenotomy  of  the  right  superior  rectus; 
but  if  the  remaining  hyperphoria  should  be  complicated 
with  plus  cyclophoria,  the  nasal  and  central  fibers 
should  be  cut,  with  the  double  purpose  of  altering  the 
tension  for  the  hyperphoria  and  changing  the  plane  for 
the  cyclophoria. 

When  sthenic  exophoria  is  complicated  by  a  plus  cyclo- 
phoria only,  the  upper  and  central  fibers  of  both  externi 
(not  one  alone)  should  be  cut.  The  triple  effect  of 
these  operations  is:  (1)  alteration  of  tension  for  the  exo- 


HETEROPHORIA.  247 

phoria;  (2)  lowering  plane  of  both  extern!  for  the  plus 
cyclophoria;  (3)  the  development  of  a  double  cataphoria, 
which,  in  itself,  is  not  bad. 

In  asthenic  exophoria,  uncomplicated,  the  tension  of 
the  interni  must  be  increased  by  shortenings  or  advance- 
ments so  done  as  not  to  change  the  plane  of  rotation. 
The  same  is  true  of  asthenic  exophoria  complicated  by  a 
hyperphoria  alone.  Later  the  hyperphoria  may  be  re- 
lieved by  a  central  partial  tenotomy  of  the  superior  rec- 
tus  of  the  hyperphoric  eye. 

When  an  asthenic  exophoria  is  complicated  with  a 
right  hyperphoria  and  a  plus  cyclophoria,  the  internus 
of  the  cataphoric  eye  should  be  so  shortened  or  advanced 
as  to  alter  its  tension,  for  the  exophoria,  and  elevate  its 
plane,  for  counteracting  the  cataphoria  and  curing  the 
plus  cyclophoria.  If  the  internus  of  the  once  hyper- 
phoric eye  must  be  shortened  or  advanced  to  still  fur- 
ther correct  the  exophoria,  not  any  longer  complicated, 
it  must  be  so  done  as  not  to  change  its  plane;  and  the 
same  is  true  if  the  only  remaining  complication  is  a  hy- 
perphoria, for  in  counteracting  the  hyperphoria,  a  plus 
cyclophoria  would  be  developed.  It  is  also  true  that 
only  the  tension  of  the  internus  should  be  altered  by  a 
shortening  or  advancement  when  the  remaining  exopho- 
ria is  complicated  by  hyperphoria  and  plus  cyclophoria, 
for  the  reason  that  lowering  the  plane  would  increase 


248  HETEROPHORIA. 

the  cyclophoria,  although  lessening"  the  hyperphoria; 
while  elevating1  the  plane  would  increase  the  hyperpho- 
ria, although  diminishing  the  cyclophoria.  Later  the 
hyperphoria  or  hyper-cyclophoria  should  be  remedied  by 
the  correct  operation  on  the  superior  rectus. 

An  asthenic  exophoria  complicated  by  a  plus  cyclopho- 
ria must  be  treated  by  such  shortening  or  advancement 
of  both  interni  as  to  alter  the  tension  for  the  exophoria 
and  elevate  both  planes  for  the  plus  cyclophoria.  The 
double  hyperphoria  resulting  would  be  counteracted  by 
a  pose  of  the  head. 

Cyclophoria  may  exist  alone  and  may  be  so  high  in  de- 
gree as  to  demand  relief  by  operation.  This  can  be  ac- 
complished by  operating  on  both  superior  or  both  infe- 
rior recti.  A  plus  cyclophoria,  uncomplicated,  can  be 
relieved  by  dividing  a  few  of  the  nasal  fibers  or  advan- 
cing a  few  of  the  temporal  fibers  of  both  superior  recti. 
In  doing  the  former  a  double  cataphoria  is  developed, 
while  the  cyclophoria  is  cured;  in  doing  the  latter  the 
cyclophoria  is  cured,  but  a  double  hyperphoria  results. 
Since  a  double  cataphoria  is  preferable  to  a  double  hyper- 
phoria, a  division  of  the  nasal  fibers  of  the  superior  recti 
should  always  be  chosen. 

The  plus  cyclophoria  can  be  cured  by  a  division  of  the 
temporal  fibers  or  an  advancement  of  the  nasal  fibers  of 
both  inferior  recti.  The  former  would  give  a  double 


HETEROPHORIA. 


249 


hyperphoria,  while  the  latter  would  give  a  double  cata- 
phoria;  hence,  of  the  two  the  latter  should  be  chosen. 
As  to  final  results,  a  division  of  the  nasal  fibers  of  the 
superior  recti  and  an  advancement  of  the  nasal  fibers  of 
the  inferior  recti  are  precisely  alike;  but  the  former 
should  be  preferred,  for  it  is  more  easily  done  and  gives 
the  patient  much  less  inconvenience. 

OPERATIONS  ON  THE  RECTI. 

The  strictest  antiseptic  precautions  must  be  observed 
in  the  preparation  of  the  patient  and  the  instruments; 
and  the  operator  and  assistant  must  have  clean,  asep- 


Fig.  36.    THE  STEVENS  SCISSORS. 

tic  hands.  Unless  the  patient  is  a  child  who  cannot  be 
controlled,  or  a  very  nervous  adult,  general  anesthesia 
should  not  be  produced.  Under  cocaine  anesthesia,  the 


Fig-  37-    THE  STEVENS  FORCEPS. 

solution  always  being  made  fresh  and  sterile  for  each 
case,  muscle  operations  are  practically  painless.     These 


250  HETEROPHORIA. 

operations  may  be  made  almost  bloodless  by  the  use  of 
two  or  three  drops  of  adrenaline  chloride  solution  (1-1000) 
dropped  into  the  eye  while  cocainization  is  being-  effected 
in  the  usual  way — one  drop  of  a  10  per  cent  solution  at 


Fig.  38.    THE  STEVENS  FORCEPS. 

intervals  of  two  minutes,  until  three  or  four  drops  have 
been  instilled.  In  five  minutes  after  the  instillation  of 
the  last  drop  of  cocaine  solution  the  operation  should  be 
commenced.  The  stop-speculum,  fixation  forceps,  Ste- 


r  iii^~ •• 

Fig-  39-    THE  STEVENS  HOOK. 

vens  scissors,  and  Stevens  hook  constitute  the  array  of 
instruments  necessary  for  doing  partial  tenotomies.  If  a 
muscle  is  to  be  advanced,  a  needle  holder,  two  small  nee- 
dles curved  at  the  point,  number  five  silk  (either  white 


Fig.  40.    THE  STEVENS  NEEDLE  HOLDER. 

or  iron  dyed),  a  large  strabismus  hook,  and  a  silver  su- 
ture plate  must  be  added  to  the  instruments  named;  and 
if  a  shortening  operation  is  to  be  done,  an  additional 
large  strabismus  hook,  or,  probably  what  would  be  bet- 


HETEROPHORIA.  25l 

ter,  the  muscle  forceps  devised  by  Clark,  of  Columbus, 
O.  Most  of  these  instruments  are  shown  in  accom- 
panying1 cuts.  The  time  occupied  in  doing  any  of  these 
operations  is  short.  The  after  treatment  consists  in 
using-  freely,  several  times  a  day,  while  the  redness  lasts, 
an  anodyne-antiseptic  wash  (Tinct.  Opii,  gtt.  xxx,Acid 
Boracic,  gr.  xx,  Dist.  water,  oz.  i).  Both  eyes  should  be 
kept  open,  to  favor  easier  binocular  adjustment.  A 
muscle  suture  should  be  removed  on  the  seventh  day,  unless 
severe  reaction  should  indicate  an  earlier  removal.  The 
Price  silver  suture  plate  does  its  best  work  in  facilitat- 
ing- the  removal  of  the  suture,  making-  this  step  painless 
as  well  as  easy.  It  prevents  the  swollen  tissue  from 
concealing-  the  knot. 

PARTIAL  TENOTOMY. 

There  are  two  kinds  of  partial  tenotomy,  central  and 
marginal.  The  indications  for  the  one  or  the  other  may 
always  be  well  understood  in  any  given  case,  as  has  been 
set  forth  in  another  part  of  this  chapter.  The  object  of 
the  central  tenotomy  is  only  to  lessen  the  tension  of  the 
muscle;  the  object  of  the  marginal  tenotomy  is  both  to 
lessen  the  tension  of  the  muscle  and  to  change  its  plane 
of  action. 

To  do  a  central  partial  tenotomy,  the  lids  must  be 
well  separated  by  the  speculum.  The  patient  must  look 


252  HETEROPHORIA. 

as  far  as  possible  in  the  direction  opposite  the  muscle  to 
be  operated  upon.  The  conjunctiva  over  the  insertion 
of  the  tendon  must  be  lifted  in  a  meridional  fold  with 
the  forceps,  and  this  must  be  snipped  with  the  scissors. 
Through  the  cut  in  the  conjunctiva  the  forceps  should 
be  made  to  grasp  the  capsule  of  Tenon,  which  in  turn 
should  be  snipped.  Through  the  openings  in  conjunctiva 
and  capsule,  the  central  fibers  of  the  tendon  should  be 
grasped  with  the  forceps  and  slightly  raised  from  the 
sclera,  so  that  they  may  be  cut  with  the  scissors  be- 
tween the  forceps  and  the  attachment,  as  close  to  the 
latter  as  possible.  Thus  the  tendon  is  buttonholed. 
If  the  operator  is  certain,  from  the  resistance  he  feels 
with  the  forceps,  that  he  is  not  too  near  either  margin 
of  the  tendon,  he  may  divide  a  few  more  fibers,  in  both 
directions,  while  still  holding  the  tendon  with  the  forceps; 
but  in  doing  so  he  takes  some  risk  of  doing  too  much. 
Now  the  forceps  should  be  laid  down  for  the  small  hook, 
•vhich  should  be  passed  through  the  buttonhole  in  the 
tendon,  first  in  one  direction,  then  in  the  other,  beneath 
the  uncut  fibers,  so  as  to  determine  the  resistance. 
Guided  by  the  hook,  the  operator  now  divides  fiber  after 
fiber  with  the  scissors,  until  the  lessened  resistance  warns 
him  that  he  has  gone  far  enough  in  that  direction.  He 
then  repeats  this  step  toward  the  other  margin  in  the 
same  careful  way.  Some  of  the  fibers  in  both  directions 


HETEROPHORIA.  253 

must  be  left  uncut,  so  as  to  act  as  stay  cords  to  prevent 
a  too  far  recession  of  the  cut  part  of  the  tendon.  The 
strength  of  the  uncut  fibers  at  the  margin  should  be  left 
as  nearly  equal  as  possible,  so  that  the  muscle  plane  may 
be  the  same  after  as  before  the  operation.  Should'  the 
fibers  be  left  stronger  at  the  one  margin  than  at  the 
other,  the  plane  will  be  certainly  shifted  toward  the 
stronger  fibers,  and  an  undesired  torsioning  effect  will 
accompany  the  lessening  of  the  tension.  To  get  the  full 
effect  of  a  partial  tenotomy,  the  capsule  of  Tenon  must 
be  cut  coextensively  with  the  division  of  the  tendon.  The 
cut  in  the  conjunctiva  may  or  may  not  be  of  the  same  ex- 
tent. There  is  no  necessity  for  making  either  a  very 
small  or  a  very  large  conjunctival  incision;  but  for  those 
just  beginning  to  operate,  a  large  conjunctival  incision 
would  make  the  tenotomy  both  easier  and  safer. 

Dr.  George  H.  Price,  of  Nashville,  has  just  invented 
an  instrument  that  may  prove  to  be  most  useful,  in  that 
it  can  measure  the  amount  of  resistance  of  uncut  fibers 
when  a  partial  tenotomy  is  being  done.  Up  to  the  pres- 
ent, operators  have  been  guided  only  by  an  indefinable 
sense  of  resistance  when  drawing  on  the  hook.  If  that 
resistance  can  be  measured — and  the  tendonometer  gives 
promise  in  that  direction — eventually  a  rule  of  practice 
may  be  established  which  will  be  valuable  to  any  opera- 
tor, whether  experienced  or  inexperienced.  Fig.  41  will 


254  HETEROPHORIA. 

give  the  reader  a  fair  understanding"  as  to  the  construc- 
tion of  the  instrument;  however,  a  description  by  the  in- 
ventor follows  : 

THE  TENDONOMETER. 

"  This  instrument,  as  its  name  implies,  is  designed  for 
measuring-  the  resistance  of  the  ocular  muscles,  either  in 
part  or  as  a  whole.  It  consists  of  a  muscle  hook  (a), 
with  graduated  shaft  (s),  which  is  suspended  by  a  coil 
spring  (c)  in  a  hollow  metal  handle  (h),  the  construction 
being  upon  the  same  general  principle  as  an  ordinary 
spring  balance.  The  hook  proper  is  5-16  of  an  inch  long 
and  nearly  straight,  so  that  it  can  be  passed  under  the 


1   I    I    I    I    I    I    .'•  I    II    I    I    I    II    I    ;    I 

I      j     3    *      j     I     7     «     j      t>    11     *     »    H     <t    It    17     )»    » 


Fig.  41.    THE  TENDONOMETER. 

tendon  when  it  is  exposed,  and  its  resistance  tested;  or  it 
can  be  passed  into  the  buttonhole  made  in  the  tendon 
when  doing  a  partial  tenotomy,  and  the  remaining  fibers 
can  be  tested,  both  those  above  and  below  the  opening 
in  the  tendon.  The  shank  of  the  hook  is  about  1  1-2 
inches  long,  and  round.  The  shaft  of  the  hook  (s)  is 
about  3  1-2  inches  long,  1-16  of  an  inch  thick,  and  3-16 
of  an  inch  wide.  The  shaft  is  graduated  on  both  sides, 
as  indicated  in  the  diagram.  At  its  upper  end  there  is  a 


HETEROPHORIA.  255 

small  eyelet  into  which  the  spring  is  caught,  by  which  it 
is  suspended  from  the  screw  (x),  which  passes  through 
the  cap  (y),  which  fits  into  the  upper  end  of  the  handle  (h). 
The  spring  is  made  of  some  material  such  as  nickel  plat- 
ed steel,  hardened  gold,  or  bronze,  to  prevent  rusting. 
The  handle  is  made  of  aluminium.  It  is  rectangular  in 
cross  section,  being  about  3-16  of  an  inch  x  1-4  of  an 
inch,  slightly  roughened  to  prevent  slipping  in  the  fin- 
gers of  the  operator.  At  (x)  the  body  of  the  handle 
is  thickened,  and  its  end  is  slotted  with  an  opening  just 
large  enough  to  admit  the  shaft  of  the  hook,  or  it  can  be 
provided  with  a  cap  which  is  slotted  and  slips  into  the 
handle,  the  cap  being  made  of  harder  metal.  The  cap  (y) 
at  the  upper  end  of  the  handle  is  made  of  hard  metal,  is 
drilled  and  tapped,  so  that  the  screw  (x)  passes  through 
this  and  can  be  screwed  in  or  out  to  adjust  the  tension 
on  the  spring  (c),  so  as  to  keep  the  zero  mark  of  the 
scale  fixed.  The  screw  (x)  will  be  provided  with  a  small 
jam  nut,  not  shown  in  the  cut,  so  that  when  the  spring 
is  set  this  nut  can  be  jammed  down  against  the  cap  (y) 
and  prevent  displacement  of  the  spring  and  shaft.  The 
graduations  upon  the  shaft  of  the  hook  will  measure  the 
units  of  resistance  of  a  tendon  or  part  of  a  tendon;  and 
the  instrument  is  designed  for  the  purpose  of  aiding  in 
the  accurate  performance  of  those  operations  which  re- 
quire a  very  delicate  sense  of  touch  on  the  part  of  the 


256  HETEROPHORIA. 

operator,  something  very  hard  to  acquire  and  not  gov- 
erned by  any  fixed  standard." 

A  skilled  operator  can  easily  grasp  conjunctiva,  cap- 
sule, and  tendon  at  the  same  time,  and  go  through  them 
all  with  one  snip  of  the  scissors.  He  then  completes  the 
operation  as  already  described. 

If  the  indication  is  for  a  marginal  tenotomy,  the  initial 
cut  of  the  conjunctiva,  capsule,  and  tendon  is  made  as  for 
a  central  tenotomy,  care  being  exercised  that  the  button- 
hole in  the  tendon,  if  not  in  the  center,  shall  be  nearer 
that  margin  which  is  to  be  completely  severed  later. 
Still  holding  the  tendon  with  the  forceps,  the  scissors 
may  be  passed  in  the  direction  in  which  complete  divi- 
sion is  indicated,  and  be  made  to  cut  all  the  fibers  at  once. 
The  hook  should  now  be  used — first,  to  determine  that 
all  the  tendon  has  been  cut  toward  the  one  margin;  and 
next,  to  test  the  resistance  of  the  uncut  fibers  at  the  other 
margin.  If  this  resistance  is  too  great — it  would  be  un- 
fortunate if  it  were  too  little — other  fibers  may  be  di- 
vided. But  a  sufficient  number  of  fibers  at  this  margin 
should  be  left  intact  to  prevent  an  over-effect.  This  op- 
eration must  not  only  lessen  the  tension  of  the  muscle  so 
as  to  favor  its  direct  antagonist,  but  it  must  also  change 
the  plane  of  its  action  so  as  to  cure  a  complicating  cy- 
clophoria. 

There  is  no  mathematical  rule  by  which  to  be  guided 


HETEROPHORIA.  257 

in  these  operations.  The  beginner  should  always  aim  at 
accomplishing-  less  than  the  effect  desired,  while  the  ex- 
pert operator  should  be  careful  not  to  do  loo  much.  In 
these  operations,  as  in  all  others,  practice  alone  can  give 
the  greatest  skill  and  the  highest  degree  of  accuracy. 

MUSCLE  SHORTENING. 

This  operation,*  rather  than  advancement,  should  be 
done  in  nearly  all  cases  of  heterophoria,  in  which  the  in- 
dication is  to  increase  the  tension  of  the  muscle.  Not 
only  can  this  operation  alter  the  tension  of  the  muscle, 
but  it  can  also  be  done  so  as,  at  the  same  time,  to  change 
its  plane  of  rotation.  Its  advantages  over  the  advance- 
ment operation  are  three:  First,  it  is  easier  of  accom- 
plishment, though  a  little  more  painful;  second,  its  plane 
of  rotation  is  less  likely  to  be  changed  when  there  is  no 
indication  for  changing  it;  third,  the  stitch  is  not  so 
likely  to  cut  its  way  out,  and  if  it  does  so,  or  if  the  knot 
should  become  untied,  the  case  would  be  no  worse  than 
before  the  operation;  whereas,  if  either  of  these  accidents 
should  happen  to  an  advancement,  before  adhesion  has 
formed,  the  recession  of  the  muscle  might  be  farther 
back  than  its  original  attachment.  However,  in  some 
cases  of  heterophoria,  in  which  the  indication  is  to  in- 

*See  Ophthalmic  Record,  March,  1893,  in  which  it  was  first  described. 


258  HETEROPHORIA. 

crease  the  tension,  the  muscle  attachment  is  so  far  back, 
or  the  muscle  itself  is  so  small,  that  an  advancement 
must  be  done. 

The  shortening  operation  for  simply  increasing"  the 
tension  of  the  muscles  is  done  as  follows:  Lids  must  be 
widely  separated  with  the  speculum.  The  conjunctiva 
must  be  seized  with  the  forceps,  so  as  to  be  thrown  into 
a  fold  parallel  with  the  corneal  margin,  behind  the  tendon 
insertion;  and  this  conjunctival  fold,  if  the  muscle  be  an 
externus  or  an  internus,  must  be  cut  with  the  scissors  a 
little  below  the  lower  border  of  the  muscle;  but  if  it  be 
a  superior  or  inferior  rectus,  the  cut  must  be  to  the  nasal 
side  of  the  muscle.  Through  this  cut  the  capsule  of 
Tenon  is  grasped  and  cut  in  line  (meridionally)  with  the 
conjunctival  cut.  Through  the  opening  thus  made,  one 
of  the  large  strabismus  hooks  is  passed  beneath  the 
muscle  and  drawn  forward  until  stopped  by  the  attach- 
ment of  the  tendon;  then,  through  the  same  opening,  the 
second  large  hook  is  passed  beneath  the  belly  of  the 
muscle  and  carried  backward,  at  the  same  time  lifting 
the  muscle  from  the  sclera,  so  as  to  show  the  extent  of 
the  possible  shortening".  If  the  opening  in  the  conjunc- 
tiva and  capsule,  by  being  too  small,  should  stop  the 
second  hook  too  soon,  it  should  be  enlarged  toward  the 
equator  by  a  cut  or  two  of  the  scissors.  Having  already 
armed  the  number  five  silk  with  two  needles,  the  operator 


HETEROPHORIA.  259 

places  one  of  them  in  the  needle  holder,  and,  passing  it 
through  the  cut  beneath  the  muscle,  forces  it  through  the 
upper  border  of  the  tendon,  close  to  the  sclera  (if  an  inter- 
nus  or  an  externus,  but  the  outer  border  if  a  superior  or 
inferior  rectus),  and  brings  it  out  at  once  through  the  cap- 
sule and  conjunctiva.  While  doing  this  the  tendon  is 
held  up  by  the  first  hook  and  the  needle  is  passed  be- 
tween this  hook  and  the  sclera.  No  other  puncture  will 
have  to  be  made  with  this  needle,  but  it  should  remain 
on  the  suture  so  as  to  facilitate  the  passing  of  that  end 
of  the  suture  through  one  of  the  holes  of  the  suture 
plate  later.  The  first  hook  remaining  under  the  tendon 
and  still  held  by  the  operator,  the  assistant  is  directed 
to  pass  the  other  hook  as  far  back  beneath  the  muscle  as 
possible,  at  the  same  time  lifting  the  muscle  well  from 
the  sclera.  The  operator,  with  the  second  needle  in  the 
holder,  passes  it  through  the  opening  beneath  the  belly 
of  the  muscle  as  far  back  as  he  wishes,  when  he  forces 
it  through  the  muscle,  then  through  the  capsule  and  con- 
junctiva, so  that  a  line  connecting  this  and  the  first  punc- 
ture shall  be  parallel  with  the  plane  of  rotation  of  this 
muscle.  The  suture  is  now  drawn  on  so  as  to  make  the 
thread  disappear  beneath  the  muscle.  The  second  needle 
is  again  placed  in  the  holder,  and  the  operator  passes  it 
through  the  conjunctiva,  capsule,  and  the  other  border 
of  the  muscle,  bringing  it  out  through  the  cut  in  the  con- 


260  HETEROPHORIA. 

junctiva  and  capsule.  The  third  puncture  is  so  made 
that  the  loop  of  thread  passing-  from  the  point  of  the 
second  puncture  to  it,  and  lying1  on  the  conjunctiva,  shall 
be  parallel  with  the  equator  of  the  eye.  Now  the  assist- 
ant's hook  may  be  removed.  The  surg-eon  aguin  places 
the  second  needle  in  the  holder  and  passes  it  through 
the  cut  beneath  the  tendon,  which  he  still  lifts  with  his 
own  hook,  and  forces  it  through  the  other  border  of  the 
tendon  close  to  its  insertion,  and  bring-s  it  out  through 
capsule  and  con-junctiva,  so  that  a  line  connecting-  the 
first  puncture  and  this,  the  fourth,  shall  be  parallel  with 
the  corneal  marg-in,  and  the  line  from  the  third  to  the 
fourth  puncture  shall  be  parallel  with  the  plane  of  rota- 
tion. Drawing-  on  this  end  of  the  suture,  that  part  of  it 
between  the  third  and  fourth  punctures  disappears  be- 
neath the  muscle.  The  operator's  hook  is  now  removed, 
and  the  two  needles,  after  being-  made  to  carry  the  two 
ends  of  the  suture  througfh  the  holes  in  the  silver  plate, 
are  also  removed.  It  only  remains  to  tie  a  surg-eon's  knot 
over  the  plate,  drawing-  sufficiently  hard  to  bring-  forward 
that  portion  of  the  muscle  lying-  beneath  the  loop  which 
rests  on  the  conjunctiva,  until  it  rests  in  contact  with  the 
tendon  at  its  insertion.  The  knuckle  of  muscle,  capsule, 
and  conjunctiva  thus  made  demands  no  attention,  since, 
in  the  course  of  a  few  weeks,  it  disappears  by  absorp- 
tion atrophy.  The  patient  will  complain  some  at  the 


HETEROPHORIA.  261 

first  two  passages  of  the  second  needle,  and  also  of  the 
drawing-  brought  about  by  tying-  the  knot.  The  after- 
treatment  is  the  same  as  that  for  partial  tenotomies. 

If  a  shortening-  is  to  be  done  so  as  not  only  to  alter  the 
tension  of  the  muscle,  but  also  to  change  its  plane  of 
rotation,  the  operation  differs  from  that  already  described 
only  in  the  making-  of  the  four  punctures  while  placing 
the  suture.  Let  the  condition  to  be  relieved  be  an  asthen- 
ic  exophoria  complicated  by  a  plus  cyclophoria,  in  short- 
ening an  internus  it  should  be  that  one  belonging  to  the 
cataphoric  eye,  provided  there  is  a  vertical  error,  other- 
wise both  interni  should  be  shortened.  The  first  needle 
should  be  passed  as  nearly  as  possible  through  the  upper 
border  of  the  tendon;  the  second  needle  should  make  its 
first  puncture  through  the  muscle  below  the  plane  bisect- 
ing it,  while  its  second  puncture  should  be  made  as  near 
as  possible  to  its  lower  border.  The  third  puncture 
with  the  second  needle  should  be  made  between  the  first 
puncture  and  the  plane  bisecting  the  attachment  of  the 
tendon.  Thus  it  will  be  seen  that  the  first  and  fourth 
punctures  are  above  the  natural  plane  of  rotation,  while 
the  second  and  third  punctures  are  below  this  plane.  In 
tying  the  knot,  the  lower  border  of  the  muscle  is  carried 
upward,  and  in  this  way  the  muscle  is  given  a  new  and 
higher  attachment,  and  thereby  the  plane  of  rotation  is 
correspondingly  elevated. 


262  HETEROPHORIA. 

If  the  external  rectus  must  be  shortened  to  cure  an 
asthenic  esophoria  complicated  by  a  plus  cyclophoria,  the 
position  of  the  punctures  should  be  reversed;  for  in  such 
a  case  the  plane  of  rotation  must  be  depressed  by  the 
creation  of  a  lower  attachment,  and  both  externi  must 
be  thus  operated  upon.  If  there  is  also  a  hyperphoria, 
this  operation  should  be  done  only  on  the  externus  be- 
longing1 to  the  hyperphoric  eye. 

If  the  superior  rectus  is  to  be  shortened  to  cure  an 
asthenic  cata-cyclophoria  of  the  eye  to  which  it  belongs, 
the  first  and  fourth  punctures  must  be  to  the  outer  side 
of  its  old  plane  of  rotation,  while  the  second  and  third 
punctures  should  be  on  the  inner  side  of  this  plane. 
Tying  the  knot  will  create  a  new  attachment  farther 
toward  the  temple  than  the  original  one.  Thus  the 
plane  of  rotation  is  shifted  out.  Just  the  reverse  must 
be  true  of  the  punctures  if  they  are  to  be  made  on  the 
inferior  rectus  with  the  view  of  curing  an  asthenic  hyper- 
cyclophoria  of  the  eye  to  which  it  belongs.  This  would 
shift  its  point  of  attachment  toward  the  nose,  carrying 
the  plane  of  rotation  with  it. 

Partial  marginal  shortenings  may  be  done  for  the  re- 
lief of  cyclophoria  when  there  is  no  special  indication  for 
altering  the  tension  of  the  whole  muscle.  In  such  an 
operation,  all  the  needle  punctures  should  be  made  on 
the  same  side  of  the  muscle  plane.  To  illustrate:  There 


HETEROPHORIA.  263 

being-  but  little  exophoria,  the  existing-  plus  cyclophoria 
may  be  cured  by  changing  the  plane  of  both  interni 
without  greatly  increasing-  the  tension  of  these  muscles. 
For  the  accomplishment  of  this  the  conjunctival  and 
capsular  cut  must  be  at  the  upper  border  of  the  muscle; 
the  needles  must  be  passed  the  four  times  entirely  in  the 
upper  half  of  the  muscle  and  tendon;  and  the  space  be- 
tw-een  the  insertion  of  the  tendon  and  the  loop  of  the  suture 
must  not  be  anything-  like  so  great  as  in  a  shortening-  of 
the  whole  muscle.  Tying-  the  knot  over  the  suture  plate 
folds  only  the  upper  part  of  the  muscle,  the  power  of 
this  part  being-  thereby  increased.  The  same  operation 
should  be  done  on  the  internus  of  the  fellow  eye. 

If  the  partial  marginal  shortening,  to  cure  a  plus  cyclo- 
phoria, is  to  be  done  on  the  externi,  the  lower  margin  of 
the  muscle  and  tendon  is  the  part  to  be  folded,  and  the 
effect  should  be  divided  between  the  two  externi.  If,  for 
the  same  condition,  the  operations  are  to  be  done  on  the 
superior  recti,  the  suture  must  be  taken  in  the  temporal 
margin  of  each;  if  on  the  inferior  recti,  the  inner  margins 
only  must  be  folded.  But  better  and  easier  than  partial 
marginal  shortenings  would  be  marginal  advancements. 

ADVANCEMENT  OPERATION. 

While  the  necessity  for  this  operation  exists  only  rarely 
in  cases  of  heterophoria,  yet  it  must  now  and  then  be 


264  HE>TEROPHORIA. 

done.  If  there  is  no  complicating-  cyclophoria,  the  ad- 
vancement must  be  made  directly  forward,  so  that  after 
the  operation  the  plane  of  rotation  shall  be  the  same 
as  before.  The  same  careful  preparation  of  patient, 
instruments,  and  hands  must  be  made  as  for  shortening-; 
and  the  same  instruments  are  needed,  except  that  only 
one  hook  will  be  required.  This  operation,  done  under 
cocaine,  is  less  painful  than  a  shortening1,  and  is  about 
as  quickly  done.  The  lids  should  be  separated  widely 
with  a  speculum.  The  conjunctiva  should  be  grasped 
in  line  with  the  center  of  attachment  of  the  tendon,  half- 
way between  the  attachment  and  the  margin  of  the  cor- 
nea, and  in  such  a  way  as  to  lift  a  meridional  fold,  which 
should  be  cut  with  the  scissors.  This  cut,  after  gaping, 
should  be  about  as  large  as  the  tendon  insertion  is  wide. 
The  posterior  flap  should  be  drawn  backward  to  a  point 
just  behind  the  insertion.  Now,  by  means  of  forceps 
and  scissors,  a  snip  should  be  made  through  the  capsule 
at  one  border  of  the  tendon,  and  through  the  opening 
thus  made  a  large  hook  should  be  passed  beneath  the 
tendon.  While  the  assistant  holds  the  conjunctival  flap 
back,  the  operator  raises  the  tendon  with  his  hook,  and 
then  passes  one  of  the  two  needles  with  which  the  suture 
is  armed,  twice  through  the  capsule  and  tendon,  so  as  to 
include  its  center,  and  a  little  way  behind  its  insertion. 
This  is  done  in  the  manner  of  taking  a  stitch  in  cloth. 


HETEROPHORIA.  265 

The  assistant  now  takes  hold  of  the  two  ends  of  the 
suture  and  draws  the  loop  well  up  against  the  under 
surface  of  the  tendon,  at  the  same  time  lifting-  the  ten- 
don slightly  away  from  the  sclera.  Aided  by  the  hook, 
the  operator  now  completely  divides  the  tendon,  at  its  in- 
sertion, with  one  or  two  snips  of  the  scissors.  The  next 
step  is  to  make  a  pouch  beneath  the  anterior  conjunctival 
flap,  which  is  easily  done  with  forceps  to  hold  and  scis- 
sors to  cut.  This  pouch  should  be  made  directly  in  front 
of  the  old  attachment,  and  neither  higher  nor  lower,  if 
the  muscle  is  an  externus  or  an  internus,  nor  farther  out 
or  in,  if  the  muscle  is  a  superior  or  inferior  rectus.  In 
either  case,  the  pouch  should  extend  up  to  the  corneal 
margin.  The  next  step  is  to  pass  the  two  needles 
through  the  posterior  conjunctival  flap  a  little  way  be- 
hind its  edge.  Now  the  operator  lifts  the  anterior  con- 
junctival flap  with  the  forceps  and  carefully  passes  one 
needle,  held  by  the  needle  holder,  into  the  pouch  already 
prepared,  and  makes  it  dip  well  into  the  sclera,  but  not 
through  it,  a  little  above  (if  it  be  the  upper  needle)  an 
imaginary  line  bisecting  the  original  attachment,  and 
only  the  slightest  distance  away  from  the  cornea.  In 
passing  out  of  the  sclera  the  needle  penetrates  the  con- 
junctiva. This  needle  is  now  held  out  of  the  way  by  the 
assistant,  while  the  operator  passes  the  second  needle 
in  the  same  way,  but  a  little  below  the  line  bisecting  the 


266  HETEROPHORIA. 

original  insertion.  The  needles  are  now  passed  through 
the  holes  in  the  silver  plate,  after  which  they  are  re- 
moved. The  assistant  now  grasps  the  conjunctiva,  cap- 
sule, and  muscle  just  behind  the  loop  and  forcibly  draws 
these  structures  well  forward,  while  the  operator  ties 
the  knot.  The  farther  the  loop  of  the  suture  is  passed 
through  the  tendon  behind  the  insertion,  the  greater  will 
be  the  effect  of  the  operation.  The  suture  passed,  as 
described  above,  the  tension  of  the  muscle  will  be  in- 
creased, but  its  plane  of  rotation  will  not  be  changed. 

Since  a  suture  thus  taken  is  not  likely  to  cut  its  way 
out,  even  to  a  small  extent,  too  much  over-effect  should 
not  be  attempted.  If  the  needles  were  not  made  to  dip 
into  the  sclera,  but  simply  passed  through  the  conjunc- 
tiva near  the  corneal  margin,  an  over-effect  would  be 
necessary,  for  the  reason  that  the  thread  will  partly  cut 
its  way  out  before  adhesion  has  formed,  allowing  some  re- 
cession of  the  advanced  tendon.  There  is  even  danger 
that  the  thread  will  cut  its  way  entirely  out  if  passed 
only  through  the  conjunctiva,  when,  of  course,  the  re- 
cession would  be  excessive.  No  advancement  operation 
is  safe  unless  the  suture  is  well  anchored  in  the  sclera. 

An  advancement  intended  not  only  to  alter  the  tension, 
but  also  to  change  its  plane  of  rotation,  differs  from  the 
operation  thus  described  only  in  selecting  the  place  for 
the  sclero-conjunctival  stitches.  If  the  muscle  to  be 


HETEROPHORIA.  267 

thus  operated  upon  is  an  interims,  and  the  exophoria  is 
complicated  by  a  left  hyper-cyclophoria,  the  one  to  be 
advanced  is  the  right  internus,  when  one  of  the  objects 
in  view  is  the  elevation  of  its  plane  of  rotation.  The 
tendon  must  be  found,  and  a  loop  of  the  suture  must  be 
passed  through  it,  as  for  a  straight-forward  advancement. 
After  completely  severing  the  tendon  from  the  attach- 
ment, the  conjunctival  pouch  must  be  made  higher  than 
the  original  attachment.  The  two  needles  must  now  be 
passed  into  the  pouch,  and  made  to  dip  into  the  sclera, 
then  out  through  the  conjunctiva,  at  chosen  points, 
higher  up  than  the  old  attachment,  and  close  to  the  cor- 
neal  margin.  On  tying  the  suture  thus  passed,  the 
muscle  is  carried  higher  up  on  the  globe,  as  well  as 
farther  forward.  Thus  its  tension  is  altered  so  as  to 
cure  the  exophoria,  and  its  plane  is  changed  so  as  to 
counteract  the  cataphoria  and  the  plus  cyclophoria. 

In  like  manner  the  plane  of  either  the  externus  or  the 
superior  or  inferior  recti  may  be  changed  by  an  advance- 
ment, the  only  difference  being,  in  cases  of  plus  cyclo- 
phoria complicating  other  phorias,  the  direction  in  which 
the  plane  is  to  be  shifted.  That  of  the  externus  must  be 
carried  lower;  that  of  the  superior  rectus,  farther  out; 
that  of  the  inferior  rectus,  farther  in. 

Marginal  advancements  may  be  done  on  both  intern! 
when  there  is  only  a  slight  asthenic  exophoria  complicated 


268  HETEROPHORIA. 

by  a  plus  cyclophoria.  In  doing-  this,  the  stitch  in  the 
tendon  should  be  in  its  upper  border;  only  the  upper 
fibers  should  be  cut  at  the  insertion,  after  which,  by 
means  of  scleral  stitches,  this  part  alone  should  be 
brought  straight  forward,  or  only  slightly  higher,  and 
not  very  far  in  advance  of  the  old  insertion. 

Similar  operations  on  the  externi,  or  on  the  superior 
and  inferior  recti,  may  be  done  under  proper  indications, 
the  operator  being  certain  that  he  has  selected  the  proper 
part  of  the  tendon  for  the  partial  advancement. 

In  all  advancement  operations  the  suture  should  be 
tied  over  the  silver  plate,  and  should  be  allowed  to  re- 
main in  place  seven  days,  so  as  to  give  enough  time  for  the 
formation  of  adhesions.  In  removing  the  suture,  care 
should  be  exercised  that  the  adhesions  may  not  be  torn 
loose. 

The  after-treatment  should  be  the  same  as  for  partial 
tenotomies;  that  is,  the  free  and  frequent  use  of  the 
antiseptic-anodyne  solution. 

Other  methods  of  making  the  advancement  operation 
might  be  given.  The  main  objection  to  the  high-and-low 
stitch  operations,  devised  and  advocated  by  Beard,  of 
Chicago,  and  Black,  of  Denver,  is  that  the  advanced 
tendon  cannot  be  accurately  placed,  so  that  in  one  case 
the  plane  of  rotation  may  be  changed,  when  it  should 
have  remained  as  before;  while  in  another  case  it  might 


HETEROPHORIA.  269 

remain  as  before,  when  it  should  have  been  changed. 
Nor  are  these  operations  so  simple  or  so  free  from  trau- 
matism  as  the  very  easy  and  safe  method  indorsed  and 
advised  in  this  chapter. 

Again,  let  it  be  said,  advancements  are  rarely  indicated 
in  the  treatment  of  heterophorias,  and,  whenever  pos- 
sible, should  be  substituted  by  the  operation  of  shorten- 
ing", which  is  easier,  safer,  and  better.  But  in  Hetero- 
tropias,  as  will  be  shown  in  Chapter  IX.,  advancements 
are  indicated  in  a  large  proportion  of  cases. 

The  best  of  all  advancement  operations,  therefore  the 
only  one  that  should  be  done,  is  the  "  flat  advancement  " 
without  severing  the  tendon,  devised  by  Lagleize.  A 
horseshoe  incision,  with  the  convexity  toward  the  cor- 
nea, should  be  made  through  the  conjunctiva  and  capsule 
of  Tenon,  from  a  point  well  in  advance  of  the  tendon  at- 
tachment, backward,  over  the  muscle  to  be  advanced, 
sufficiently  far  to  expose  that  part  of  the  muscle  through 
which  the  loop  of  the  suture  must  be  passed.  The  as- 
sistant must  hold  this  flap  out  of  the  way  by  means  of  a 
forceps.  The  operator  then  passes  a  large  strabismus 
hook  beneath  the  tendon,  and  draws  it  well  up  against 
the  insertion  of  the  tendon.  Next  he  passes  a  second 
large  hook  beneath  the  tendon  and  carries  it  backward 
beneath  the  belly  of  the  muscle  to  a  point  beyond  where 
he  expects  to  pass  the  loop  of  suture.  He  now  places 


270  HETEROPHORIA. 

the  second  hook  in  the  hand  of  the  assistant,  who  gently 
lifts  the  muscle  away  from  the  globe.  With  the  first 
hook  the  operator  steadies  the  eye  while  passing"  the 
suture  through  the  muscle,  which  he  may  do  in  one  of 
two  ways:  (1)  He  may  take  the  muscle  part  of  the  stitch 
with  only  one  of  the  two  needles  with  which  the  suture 
is  armed,  by  passing  it  through  the  muscle  near  one  bor- 
der and  bringing  it  out  at  a  point  directly  opposite,  near 
the  other  border.  Drawing  the  suture  after  the  needle 
thus  passed  places  the  loop  beneath  the  belly  of  the 
muscle.  Or  (2)  he  may  pass  one  needle  beneath  the  mus- 
cle and  force  it  through  near  the  far  border,  and  then 
pass  the  second  needle  through  the  near  border,  from 
beneath,  at  a  point  directly  opposite  the  puncture  of  the 
other  needle.  Drawing  the  suture  after  the  two  needles 
places  the  loop  beneath  the  belly  of  the  muscle,  as  if  it 
had  been  taken  with  one  needle,  as  described  in  (1). 
This  loop  must  always  be  just  as  far  behind  the  inser- 
tion of  the  tendon  as  the  later  scleral  stitches  shall  be  in 
front.  The  muscle  part  of  the  suture  having  been 
passed,  the  two  hooks  should  be  removed.  The  next 
step  of  the  operation  is  the  passing  of  both  needles 
through  the  anterior  margin  of  the  capsulo-conjunctival 
flap.  The  operation  must  be  completed  without  cutting- 
the  tendon.  To  enable  him  to  pass  easily  the  scleral 
stitches,  the  operator  fixes  the  eyeball  by  firmly  grasp- 


HETEROPHORIA.  271 

ing,  with  fixation  forceps,  the  exposed  tendon  at  its  in- 
sertion, and  then  passes  first  one  needle  and  then  the  other 
deep  into,  but  not  through,  the  sclera,  at  points  just  as 
far  in  advance  of  the  tendon  insertion  as  the  loop  is  be- 
hind it.  The  scleral  stitches  are  to  be  neither  hig-her 
nor  lower  than  the  two  points  of  passing-  of  the  muscle 
part  of  the  suture,  if  the  rotation  plane  of  the  muscle  is 
not  to  be  chang-ed.  The  needles  should  now  be  passed 
throug-h  the  two  holes  of  the  Price  suture  plate,  after 
which  they  should  be  removed.  In  tying-  the  surg-eon's 
knot  on  the  silver  plate,  the  muscle  is  carried  over  its 
attachment  until  that  part  throug-h  which  the  loop  was 
passed  is  at  the  line  of  the  two  scleral  punctures,  and  it 
is  kept  there  by  the  completion  of  the  knot-  The  cap- 
sulo-conjunctival  flap  completel}T  covers  the  operative 
field  by  having-  been  included  in  the  suturing-.  The 
stitches  must  be  allowed  to  remain  seven  days. 

If  the  rotation  plane  of  the  muscle  must  be  chang-ed, 
the  scleral  punctures  must  be  made  in  the  direction  in- 
dicated in  any  g-iven  case. 

There  is  no  advancement  operation  that  will  compare 
with  the  "flat  advancement"  operation  of  Lag-leize,  in 
the  ease  with  which  it  is  done,  in  simplicit}',  and  in  safe- 
ty; but  even  this  operation  should  be  done  only  when 
more  effect  is  needed  than  can  be  g-otten  from  the  sim- 
pler and  safer  operation  of  tucking-,  or  folding-,  or  short- 


272  HETEROPHORIA. 

ening,  devised  by  the  author,  but  erroneously  claimed  by 
sundry  others.  The  shortening1  operation  is  fully  de- 
scribed on  pages  257  to  263. 

In  the  treatment  of  heterophoric  conditions  by  any 
method  outlined  in  this  chapter,  the  aim  is  to  relieve  the 
basal  or  fusion  brain-centers  from  abnormal  work,  by 
giving"  equal  tonicity  to  the  two  muscles  of  any  pair — 
the  establishment  of  orthophoria. 

To  withhold  the  treatment  indicated  in  any  given  case 
of  heterophoria  is  unjust  to  the  patient  and  will  be  hurt- 
ful to  the  practitioner.  The  day  has  forever  passed 
when  an  oculist  can  securely  boast  of  ignorance  of  heter- 
ophorias,  on  his  own  part,  and,  in  turn,  speak  dispara- 
gingly of  others  who  claim  to  know.  Confession  of  ig- 
norance on  his  own  part  disqualifies  one  for  passing  un- 
favorable judgment  on  others  who,  by  means  of  hard 
study  and  close  observation,  have  a  right  to  claim  that 
they  know. 


CHAPTER  IV. 


ESOPHORIA. 


THERE  is  an  esophoria  which,  because  of  its  nature,  may 
be  called  "true,"  or  "intrinsic;"  while  there  is  another 
form  that  should  be  termed  "  pseudo."  The  one  kind  is 
entirely  distinct  from  the  other,  and  yet  the  two  often  co- 
exist, the  one  being-  grafted  on  to  the  other.  Whatever 
may  be  the  kind  of  esophoria,  there  is  a  tendency  on  the 
part  of  the  interni  alone,  or  with  the  aid  of  their  syner- 
gists,  to  converge  the  visual  axes  at  a  point  between  the 
observer  and  the  object  fixed;  but  this  too  near  intersec- 
tion of  the  visual  axes  is  prevented  by  excessive  nerve 
impulses  sent  to  the  antagonizing  muscles,  increasing 
their  tension  abnormally.  In  the  interest  of  binocular 
single  vision  the  too  great  inherent  tension  of  the  interni 
is  counteracted  by  a  corresponding  nervous  tension  of 
the  externi. 

INTRINSIC  ESOPHORIA. — In  this  condition  the  interni 
have  an  advantage  over  the  externi,  which  may  be  due 
to  any  one  of  several  conditions.  It  may  be  that  the  in- 
terni are  over-developed,  or,  what  would  result  in  the 
same  thing,  the  externi  may  be  under-developed.  In 

(278) 


274  ESOPHORIA. 

either  case  there  would  be  an  imbalance  in  favor  of  the 
interni.  That  this  is  often  true  hardly  admits  of  a  doubt; 
for  every  surgeon  who  has  operated  often  will  testify 
that,  in  operating  on  the  internus  to  lessen  its  tension, 
he  has  frequently  found  it  very  large  and  strong,  and 
that,  in  operating  on  the  externus  to  increase  its  tension, 
he  has  found  it  small  and  weak. 

The  interni  may  not  be  over-developed,  but  abnor- 
mally short;  or  the  externi  may  be  abnormally  long,  thus 
giving  an  imbalance  in  favor  of  the  interni.  In  oper- 
ating on  an  internus  to  lessen  its  tension,  it  is  sometimes 
found  to  be  tense,  as  if  stretched;  while  in  operating  on 
an  externus  to  increase  its  tension,  this  muscle  is  found 
loose  and  flabby. 

The  interni  may  not  be  over-developed  nor  the  ex- 
terni under-developed,  nor  may  the  interni  be  too  tense 
while  the  externi  are  too  lax.  The  esophoria  found  in 
such  a  case  would  be  due  to  the  interni  having  their  at- 
tachments too  far  forward,  while  the  externi  have  their 
attachments  too  far  removed  from  the  corneal  margin. 

If  either  of  the  conditions  mentioned  above  should  be 
the  cause  of  an  esophoria,  it  can  be  understood  readily 
how  the  esophoria  may  be  greater  in  the  one  eye  than  in 
the  other,  and  that  it  may  exist  only  in  one  eye,  the  lat- 
eral muscles  of  the  other  eye  being  perfectly  balanced. 
This  can  be  determined  quickly  and  accurately  by  means 


ESOPHORIA.  275 

of  the  monocular  phorometer,  the  binocular  phorometer 
being  wholly  unreliable  for  this  purpose. 

Whatever  may  be  the  cause,  esophoria  is  usually  about 
equal  in  the  two  eyes.  Regardless  of  the  existence  of 
the  one  or  the  other  of  the  four  causes  discussed,  or  that 
two  or  more  of  them  may  coexist,  the  treatment,  as  will 
be  shown,  must  be  directed  either  toward  the  interni 
with  the  view  of  lessening  their  tension  by  partial  tenoto- 
mies,  or  toward  the  externi  with  the  view  of  increasing 
their  power  by  means  of  exercise  or  by  shortening  or  ad- 
vancing one  or  both  of  them.  In  low  degrees  of  the  er- 
ror, prisms  in  positions  of  rest  for  the  weak  externi  may 
be  tried. 

True,  or  intrinsic,  esophoria  may  not  depend  on  either 
one  of  the  four  causes  mentioned,  but  may  be  caused  by 
a  naturally  over-developed  third  conjugate  innervation 
center  which,  without  being  over-stimulated,  continu- 
ally, during  waking  hours,  is  sending  excessive  nerve 
impulses  to  the  otherwise  normal  interni,  to  counteract 
which,  over-stimulation  of  the  centers  controlling  the  ex- 
terni is  demanded;  or  there  may  be  an  under-develop- 
ment  of  the  centers  controlling  the  externi,  requiring 
that  these  shall  be  over-stimulated  in  order  that  a  nerve 
impulse  sufficiently  strong  shall  be  sent  to  the  externi  to 
counteract  the  normal  impulse  sent  to  the  interni.  The 
third  conjugate  innervation  center  is  wholly  undeveloped 


276  ESOPHORIA. 

in  some  cases,  there  being-  entire  absence  of  power  to 
converge;  in  other  cases  it  appears  that  this  center  is 
not  fully  developed;  hence  it  is  reasonable  to  conclude 
that  now  and  then  an  over-development  of  this  center 
exists.  If  so,  the  esophoria  is  as  true,  or  intrinsic,  as  if 
the  muscles  themselves  were  at  fault.  There  may  be, 
or  there  may  not  be,  a  conjugate  innervation  center  for 
the  externi;  but,  if  so,  it  is  only  intended  that  it  shall 
force  the  externi  to  counteract-  the  tendency  on  the  part 
of  the  interni  to  make  the  visual  axes  cross  too  soon.  It 
would  not  be  in  the  interest  of  binocular  single  vision 
for  a  conjugate  divergence  brain  center  to  exist,  hence 
the  supposition  that  there  is  no  such  center. 

Unless  one  or  more  of  the  above-mentioned  causes  ex- 
ists, there  can  be  no  such  thing  as  an  intrinsic  esophoria. 
The  superior  and  inferior  recti,  when  attached,  in  great- 
er part,  on  the  nasal  side  of  the  vertical  meridian  of  the 
eye,  act  as  a  secondary  cause  of  true  esophoria. 

Malformation  of  the  orbits  cannot  have  much  to  do, 
directly,  with  the  causation  of  intrinsic  or  even  pseudo- 
esophoria.  As  has  been  shown  in  Chapter  I.,  the  an- 
gle of  convergence  for  eyes  that  are  wide  apart  is  but 
little  greater  than  the  angle  of  convergence  when  the 
eyes  are  close  together,  and  yet  that  little  may  consti- 
tute one  of  the  factors  in  the  production  of  an  esophoria, 
or,  vice  versa,  of  an  exophoria.  When  the  eyes  are  3 


ESOPHORIA.  277 

inches  apart  and  the  point  of  fixation  is  16  inches,  the 
angle  of  convergence  is  10.7°,  while  the  angle  of  con- 
vergence for  the  same  point,  the  eyes  being  2  inches 
apart,  would  be  7.16°,  a  difference  of  3.54°.  It  is,  there- 
fore, reasonable  to  conclude  that  a  muscle  adjustment 
that  would  give  orthophoria  when  the  eyes  are  3  inches 
apart  would  give  esophoria  if  they  were  only  2  inches 
apart.  It  is  also  reasonable  to  conclude  that  a  muscle 
adjustment  that  would  give  orthophoria,  the  base-line 
being  2  inches,  would  give  exophoria  if  the  base-line 
were  3  inches.  Malformation  of  the  orbit  must  play 
only  a  very  small  part  in  the  production  of  an  esophoria 
or  an  exophoria. 

STHENIC  ESOPHORIA. — The  quantity  of  the  esophoria 
does  not  determine  its  character  with  any  certainty.  If 
the  error  is  sthenic  in  character,  it  can  be  told  only  by 
resorting  to  the  duction  and  version  tests.  How  to 
make  these  tests  has  been  fully  set  forth  in  Chapter  II. 
and  Chapter  III.;  and  so  important  are  these  tests, 
from  a  therapeutic  standpoint,  they  can  never  be  safely 
neglected.  In  sthenic  esophoria  adduction  should  be 
more  than  25°,  and  adversion  should  be  more  than  50°. 
Abduction  and  abversion  may  be  only  little  less  than 
normal,  and  rarely  would  these  exceed  the  normal. 
More  dependence  must  be  placed  on  abduction  and  ab- 
version than  on  adduction  and  adversion  in  determining 


278  ESOPHORIA. 

if  an  esophoria  is  sthenic.  If,  in  a  case  of  esophoria,  ab- 
duction and  abversion  are  nearly  normal,  it  is  of  the 
sthenic  type. 

ASTHENIC  ESOPHORIA. — Here,  again,  it  is  not  the 
quantity  of  the  error  that  determines  its  character.  It  is 
only  by  the  duction  and  version  tests  that  the  asthenic 
may  be  distinguished  from  the  sthenic.  In  such  a 
case  the  adduction  power  is  less  than  25°,  and  the  ad  ver- 
sion is  less  than  50°.  Abduction  and  abversion  will  be 
correspondingly  low.  If  in  responding  to  these  tests  a 
patient  should  show  less  duction  and  version  power  than 
he  really  has,  the  error  will  be  on  the  safe  side.  In  as- 
thenic esophoria  the  intern!  should  never  be  operated 
upon.  What  to  do  for  such  cases  will  be  fully  set  forth 
under  the  head  "Treatment." 

PSEUDO-ESOPHORIA. — As  its  name  implies,  it  is  an 
esophoria  that  has  neither  of  the  above-mentioned 
causes.  It  is  wholly  dependent  on  the  relationship  that 
exists  between  the  third  conjugate  innervation  center 
and  the  center  controlling  the  ciliary  muscles.  It  is  never 
found  in  a  myope;  it  is  never  shown  in  the  distant 
test  when  the  patient  is  an  emmetrope.  Even  an  emme- 
trope  may  show  a  pseudo-esophoria  in  the  near,  but 
only  when  the  ciliary  muscles  are  weak  and  must  re- 
ceive an  abnormal  impulse  in  order  to  focus  near  objects. 
Pseudo-esophoria  always  exists  in  cases  of  hyperopia, 


ESOPHORIA.  279 

manifesting-  itself  in  one  of  three  ways:  first,  lessening- 
the  quantity  of  an  intrinsic  exophoria;  second,  showing- 
an  esophoria  when,  in  reality,  there  is  no  imbalance  be- 
tween the  lateral  recti;  third,  showing-  a  greater  quan- 
tity of  esophoria  than  really  exists.  Thoug-h  false  in 
character,  it  is  nevertheless  harmful,  unless  it  compli- 
cates an  exophoria.  Then,  as  will  be  shown  in  the 
chapter  on  exophoria,  it  is  helpful  in  the  absence  of  any 
treatment  of  the  exophoria. 

Bonders  was  rig-ht  when  he  emphasized  the  influence 
that  accommodation  has  over  converg-ence,  thoug-h  some 
have  doubted  that  there  is  any  truth  in  his  teaching-  on 
this  subject.  He  may  have  attached  too  much  impor- 
tance to  it;  doubtless  he  did  g-o  be}Tond  bounds  when  he 
taug-ht  that  hyperopia  was  the  chief  cause  of  internal 
strabismus.  Some  idea  of  the  probable  effect  that  ac- 
commodation has  over  convergence  may  be  obtained  by 
the  study  of  eyes  that  are  emmetropic  and  orthophoric. 
Such  eyes  accommodate  3  D  for  a  distance  of  13  inches. 
The  distance  between  the  centers  of  the  eyes  being-  2-1 
inches,  the  angle  of  converg-ence  for  13  inches  will  be 
11°.  Each  eye  accommodates  3  D,  and  its  visual  axis  is 
turned  toward  the  median  plane  of  the  head  throug-h  an 
arc  of  5.5°,  showing-  nearly  2°  of  converg-ence  for  1  D  of 
accommodation  as  the  normal.  This  holds  almost  true 
when  the  accommodation  is  1  D,  the  point  of  fixation  be- 


280  ESOPHORIA. 

ing  at  a  distance  of  1  M.  The  base-line  being  2i  inches, 
the  angle  of  convergence  will  be  3:6°,  half  of  which 
(1.8°)  will  show  the  converging  of  each  axis  toward  the 
extended  median  plane  of  the  head.  To  show  how 
nearly  the  proportion  holds  good,  the  following  is  given: 
3  D:  5.5°  : :  1  D:  1.8°.  Thus  it  would  appear  thai 
1  D  of  hyperopia  would  give  1.8°  of  pseudo-esophoria, 
the  proportion  practically  holding  good  up  to  6  D,  there 
being  a  variation  of  only  .1°.  In  6  D  of  hyperopia  the 
pseudo-esophoria  for  each  dioptre  would  be  1.9°. 

A  pseudo-esophoria  may  be  chargeable,  in  some  unac- 
countable way,  to  a  complicating  plus  cyclophoria.  This 
surmise  becomes  stronger  since  it  is  well  known  that  an 
esotropia  occasionally  has  for  one  of  its  causative  factors 
a  plus  cyclophoria,  which  must  be  corrected  to  make  it 
possible  for  the  esotropia  to  be  cured.  There  must  be, 
however,  an  intrinsic  esophoria,  which  is  only  aggravated 
by  the  cyclophoria. 

In  many  cases  of  esophoria  the  distant  test  shows  a 
greater  error  than  the  test  in  the  near,  and  in  some  cases 
an  esophoria  is  shown  in  the  distant  test  and  an  exo- 
phoria  in  the  near.  Occasionally  the  esophoria  shown  in 
the  near  test  is  from  1°  to  10°  greater  than  that  shown 
in  the  far  test.  This  variation  will  not  show  itself 
when  the  esophoria  is  wholly  intrinsic.  If  there  is 
emmetropia,  the  esophoria  in  the  distant  test  is  intrinsic. 


ESOPHORIA.  281 

and  the  same  quantity  of  the  error  will  be  shown  in  the 
near  test,  if  the  ciliary  muscles  are  ideal  in  structure 
and  size  and  ready  to  g-ive  full  response  to  the  normal 
stimulus  sent  to  them  from  the  brain-center  that  controls 
their  action,  when  accommodating-  for  the  near  point.  If 
the  point  to  be  fixed  is  16  inches  from  the  eyes,  the 
impulse  sent  from  the  brain  to  the  ciliary  muscles  will 
be  a  2-50  D  impulse  and  the  muscles  will  respond  so  as 
to  increase  the  refraction  of  the  lenses  2.50  D.  The 
associated  impulse  sent  to  the  interni,  the  distance  be- 
tween the  eyes  being-  2  2  inches,  would  be  enough  to 
make  the  two  visual  axes  swing-  toward  each  other  4.5°, 
so  that  the  ang-le  of  convergence  would  be  9°  (a  small 
fraction  less).  If  the  diplopia  test  in  the  distance 
shows  6°  of  esophoria,  the  near  test  will  show  the 
same,  for  nothing  exists  to  break  the  evenness  of  the 
error.  In  another  case  of  emmetropia,  suppose  the 
ciliary  muscles  to  be  subnormal  in  their  development,  so 
that  more  than  a  2.50  D  impulse  must  be  sent  from  the 
brain-center  in  order  to  make  them  respond  sufficiently 
to  increase  the  refraction  of  the  lenses  2.50  D.  For  the 
sake  of  arg-ument,  let  a  nerve  impulse  of  5  D  be  neces- 
sary to  elicit  a  2.50  D  response  on  the  part  of  the  ciliary 
muscles;  the  associated  impulse  sent  to  each  internus 
would  be  double  that  of  the  normal  (4.5°  X  2  =  9°)  in 
the  effort  to  accommodate  at  16  inches.  The  distant 


282  ESOPHORIA. 

test  showing-  6°  of  esophoria,  the  near  test  would  show 
10.5°  of  esophoria  (6°  intrinsic  esophoria  +  4.5°  pseudo- 
esophoria  =  10.5°). 

In  another  case  of  emmetropia,  suppose  the  ciliary 
muscles  to  be  hyper-developed,  so  that  only  a  1.25  D 
nerve  impulse  is  necessary  to  elicit  a  2.50  D  response  by 
the  ciliary  muscles;  the  associated  impulse  sent  to  the 
interni  would  be  just  half  the  normal  (4.50°  -4-  2  =  2.25°) 
when  accommodating  for  a  point  at  16  inches.  The 
deficiency  of  associated  impulse  must  be  supplied  by  a 
corresponding1  amount  of  the  inherent  tension  of  the 
interni,  diminishing1  the  esophoria  in  the  near  test  just 
to  that  extent.  To  the  convergence  impulse  (2.25°) 
must  be  added  2.25°  of  the  esophoria  in  order  to  have 
the  visual  axes  form  an  angle  of  convergence  of  9°. 
Then,  the  distance  test  showing  6°  of  esophoria,  the  near 
test  would  show  3.75°  of  esophoria  (6° -2. 25°  =  3.75°). 

In  still  another  case  of  emmetropia,  there  may  be  an 
intrinsic  esophoria  of  2°  in  the  distance.  The  ciliary 
muscles  may  be  such  as  to  require  only  a  1  D  impulse  to 
call  forth  2.50  D  of  activity  on  the  part  of  hyper-devel- 
oped ciliary  muscles,  in  accommodating  for  16  inches. 
The  associated  impulse  sent  to  the  interni  would  be  only 
1.8°,  when  an  impulse  of  4.5°  is  required  for  convergence 
at  16  inches.  When  the  whole  of  the  2°  of  intrinsic  ten- 
sion of  the  interni  is  used  in  aiding  convergence,  the 


ESOPHORIA.  233 

guiding-  sensation  must  make  a  special  call  on  the  third 
innervation  center  for  .7°  more  of  convergence  on  the 
part  of  each  internus  in  order  that  the  proper  angle  of 
convergence  may  be  formed  (associated  impulse  1.8°  -f 
2°  intrinsic  esophoria  -f  .7°  extra  impulse  from  the  third 
conjugate  center  =  4.5°).  The  diplopia  test  in  the  near 
withdraws  the  extra  impulse  from  the  third  conjugate 
center  and  exophoria  of  .7°  is  shown. 

It  is  not  the  response  of  the  ciliary  muscles  in  diop- 
tre changes  of  the  lenses  that  causes  a  definite  asso- 
ciated contraction  of  the  interni,  but  it  is  the  greater 
or  smaller  impulse,  measured  in  dioptres,  generated 
by  the  brain  -  center  controlling  the  ciliary  muscles, 
that  develops  the  associated  action  of  the  interni;  for 
every  1  D  of  ciliary  impulse  there  is  1.8°  of  convergence 
impulse. 

Experiments  and  observation  do  not  show  that  an 
associated  nerve  impulse  is  sent  to  the  ciliary  muscles 
from  the  center  controlling  them  because  of  an  over- 
stimulation  of  the  third  conjugate  innervation  center. 
This  would  be  shown  in  spasm  of  accommodation — 
pseudo-myopia — a  condition  never  seen  in  cases  of  eso- 
phoria, and  rarely  seen  at  all,  even  in  a  case  of  exo- 
phoria. The  condition  so  often  spoken  of  as  spasm  of 
accommodation  is  not  such,  but  is  the  temporary  con- 
tinuance of  the  manifestation  of  an  acquired  tonicity  of 


284  ESOPHORIA. 

the  ciliary  muscles,  when  one  begins  the  wearing1  of  con- 
vex lenses  for  the  correction  of  hyperopia. 

Whatever  may  be  true  of  other  associated  brain-cen- 
ters, it  appears  that  the  center  of  the  ciliary  muscles 
and  the  third  conjugate  innervation  center  can  have  the 
associated  impulse  run  in  only  one  direction;  that  is, 
from  the  former  to  the  latter. 

TESTS  FOR  ESOPHORIA. 

No  test  for  esophoria  can  be  relied  on  when  the  eyes 
are  under  the  influence  of  a  mydriatic.  Within  an  hour, 
and  it  may  be  for  a  much  longer  time,  after  the  instilla- 
tion of  a  mydriatic,  the  third  conjugate  innervation  cen- 
ter is  excessively  stimulated,  either  directly  or  indirectly, 
more  likely  the  latter,  so  that  an  esophoria  will  be 
shown  when  there  is  none;  existing  esophoria  will  be 
increased  more  or  less;  and  an  exophoria  will  be  made  to 
appear  less  than  it  really  is.  All  of  these  statements 
are  certainly  true,  in  both  the  far  and  the  near  tests,  if 
the  patient  is  a  hyperope;  they  are  true  in  the  near,  if 
not  in  the  far,  if  the  patient  is  an  emmetrope;  they  are 
also  true  in  the  near,  if  not  in  the  far,  if  the  patient  is  a 
myope  of  less  than  2.50  or  3  D. 

The  explanation  for  this  phenomenon,  given  by  the 
author  in  1892,  he  still  believes  to  be  true.  This  ex- 
planation is  as  follows: 


ESOPHORIA.  285 

A  very  peculiar  feature  of  the  use  of  a  mydriatic  is 
that  at  first — probably  from  one  to  several,  hours — a 
mydriatic,  in  hypermetropic  eyes,  will  increase  the  eso- 
phoria,  will  lessen  an  exophoria  or  convert  it  into  ortho- 
phoria,  or  even  into  an  esophoria.  Until  now  this  has 
been  unexplained.  The  following-  explanation  must  be 
true:  The  mydriatic  acts  on  either  the  ending's  of  the 
accommodative  nerve  fibers  or  on  the  fibers  of  the 
muscle  of  accommodation,  certainly  not  on  the  accommo- 
dative center,  which,  therefore,  must  remain  in  a  state 
susceptible  of  excitation  by  the  demands  from  the  guid- 
ing- sensation.  As  the  muscles  of  accommodation  pass 
into  their  forced  rest,  the  retinal  images  become  less 
sharp  in  outline,  the  blurring  increasing  up  to  the  point 
of  full  suspension  of  accommodation.  The  guiding  sen- 
sation calls  on  the  accommodative  center  for  sharper 
images,  and  the  impulse  is  sent  out,  but  finds  the  mus- 
cles unresponsive;  the  call  is  repeated  more  eagerly,  and 
a  stronger  impulse  is  sent  to  the  sleeping  muscles,  and 
still  no  change  is  effected  in  the  images;  and  thus  the 
calls  and  the  responses  are  kept  up  for  a  longer  or  a 
shorter  time.  For  every  degree  of  activity  thus  excited 
in  the  accommodative  center,  there  is  a  corresponding 
tendency  to  activity  generated  in  the  converging  center. 
So  long  as  the  calls  are  made  on,  and  responses  are  made 
by,  the  accommodative  center,  the  center  of  convergence 


286  ESOPHORIA. 

stands  ready  to  call  into  unusual  action  the  interni, 
which  they  do  the  moment  the  guiding-  sensation  is 
robbed  of  its  restraining1  power  by  the  test  for  hetero- 
phoria,  when  an  increased  pseudo-esophoria  is  shown. 
But  finally  the  guiding  sensation  ceases  its  calls,  or, 
from  exhaustion,  the  accommodative  center  ceases  to  re- 
spond, and  now  the  normal  muscular  condition  is  again 
shown,  and  will  remain  manifest,  although  the  mydriatic 
may  be  continued.  From  this  observation  on  the  myd- 
riatic as  a  disturber  of  the  salutary  relationship  of  the 
centers  of  accommodation  and  convergence,  we  deduce 
the  following-  conclusion:  All  tests  for  lateral  hetero- 
phoria  are  wholly  unreliable  within  the  first  few  hours 
after  eyes  have  been  brought  under  the  influence  of  a 
mydriatic. 

TESTS. 

The  exclusion  test  will  always  show  an  outward  re- 
setting- whenever  the  card  is  removed.  The  resetting 
may  be  so  slig-ht  as  not  to  be  detected  objectively;  but 
the  patient  will  always  be  conscious  of  the  apparent 
movement  of  the  test  object  toward  the  opposite  side, 
however  slight  may  be  the  esophoria. 

The  red-glass  test,  by  taking  the  eye  slightly  off  its 
guard  because  of  the  change  in  the  color  of  the  image, 
will  result  in  diplopia  in  many  cases,  the  red  light  ap- 


ESOPHORIA.  287 

pearing-  on  the  side  corresponding-  to  the  eye  before  which 
the  red  glass  is  held — homonymous  diplopia.  It  will 
be  distant  from  the  true  candle,  more  or  less,  depending 
on  the  quantity  of  the  error.  The  diplopia  developed 
by  the  red  glass  practically  always  indicates  that  an 
operation  should  be  done,  but  it  does  not  determine  the 
muscle  to  be  operated  upon  nor  the  kind  of  operation  to 
be  done.  This  can  be  shown  only  by  the  duction  and 
version  tests  of  both  the  interni  and  the  externi. 

The  double  prism,  held  with  the  'line  of  union  of  the 
bases  horizontal,  shows  the  middle,  or  true,  object  dis- 
placed toward  the  corresponding  side;  or,  if  the  true 
object  be  fixed,  the  upper  and  lower  false  object  will  ap- 
pear on  the  side  corresponding  to  the  position  of  the  dou- 
ble prism.  A  prism  from  the  refraction  case  that  places 
the  false  and  true  objects  in  a  vertical  line,  measures  the 
error,  but  does  not  indicate  the  method  of  procedure  to 
be  adopted  for  effecting  a  cure.  The  duction  and  ver- 
sion powers  must  be  taken. 

If  the  single  prism  be  correctly  held  before  the  eye- 
that  is,  the  axis  vertical  and  the  base  up — the  resulting 
diplopia  will  be  homonymous;  and  the  extent  of  the  devi- 
ation can  be  measured  by  prisms,  as  when  the  Maddox 
double  prism  is  made  the  means  of  producing  the  diplo- 
pia. The  double  prism  has  the  advantage  over  the  sin- 
gle prism,  whether  they  are  placed  in  a  trial  frame  or  held 


288  ESOPHORIA. 

in  the  hand,  in  that  the  examiner  can  always  be  certain, 
with  the  double  prism,  that  its  axis  is  vertical,  when  the 
two  resulting-  images  are  made  to  appear  the  one  di- 
rectly over  the  other.  With  the  single  prism  there  is  no 
such  means  of  knowing  the  exact  position  of  the  axis, 
hence  the  chance  for  the  creeping  in  of  an  error  that,  on 
the  one  hand,  may  show  more  esophoria,  while,  on  the 
other  hand,  it  may  show  less,  than  really  exists.  The 
ease  with  which  this  source  of  error  might  be  eliminated 
by  the  double  prism  was  really  the  thought  that  led 
Maddox  to  invent  it.  Of  the  two  means  for  developing 
diplopia  by  prisms,  independent  of  the  phorometer  armed 
with  the  spirit  level,  the  double  prism  is  by  far  the 
better  and  more  reliable. 

The  Maddox  rod  was  invented  because  of  a  defect  in 
the  double  prism  as  first  made,  and  as  made  even  now 
by  some  manufacturers.  The  grinding  of  both  prisms 
on  one  piece  of  glass  left  a  somewhat  rounded  line  of 
union  of  the  bases,  so  that  not  only  would  the  candle 
blaze  be  doubled  when  the  base-line  passed  across  the 
pupil,  but  a  streak  of  light,  formed  by  the  refraction  of 
the  rays  passing  through  the  rounded  line  of  union,  ex- 
tends more  or  less  completely  from  the  one  false  light  to 
the  other.  The  streak  served  a  good  purpose,  in  that 
it  led  to  the  invention  of  the  indispensable  rod;  but 
since  it  can  no  longer  serve  a  good  purpose,  it  should 


ESOPHORIA. 


239 


be  eliminated  by  uniting-  two  separate  prisms,  base  to 
base. 

While  there  is  but  one  certain,  therefore  legitimate, 
use  for  the  Maddox  rod  —  viz.,  in  testing1  the  oblique 
muscles  —  it  is,  nevertheless,  frequently  used  in  testing 
the  recti. 

When  the  rod  is  horizontal  before  the  rig-ht  eye,  the 
vertical  streak  of  light  is  seen  to  the  rig-ht  of  the  candle 


UEFT 


RIGHT 

Fig.  42.    RETINAL  FUSION  AREAS. 

in  every  case  of  esophoria.  The  prism,  base  out,  that 
causes  the  streak  to  pass  down  through  the  light  meas- 
ures, but  not  accurately,  the  quantity  of  the  esophoria. 
The  want  of  accuracy  is  due  to  the  fact  that  the  vertical 
retinal  meridian  is  not  turned  so  far  out,  by  contraction 
of  the  internus,  as  to  throw  the  streak  entirely  outside 


290  ESOPHORIA. 

the  retinal  area  in  which  resides  the  guiding-  sensation; 
therefore  there  would  be  some  effort  made  at  fusing 
the  part  of  the  much-changed  image  with  the  true  and 
unchanged  image  in  the  other  eye.  Fig.  42  shows  this 
better  than  words  can  possibly  portray.  The  figure 
also  shows  how  a  displacing  prism,  with  base  up,  would 
throw  the  unchanged  image  of  the  candle  blaze  above 
and  entirely  beyond  the  fusion  area,  so  that  no  effort 
would  be  made  by  the  eye  to  disturb  the  position  of 
equilibrium  into  which  it  has  turned.  It  will  be  seen 
also  that  the  rotary  prism  would  carry  the  displaced 
image  to  the  vertical  meridian  without  having  it  infringe 
anywhere  on  the  fusion  area.  The  dotted  line  from  e 
represents  the  line  of  travel  of  the  image  while  the 
measurement  of  the  error  is  being  taken  with  the  rotary 
prism.  At  no  time  would  a  fusion  impulse  be  excited. 
Not  so  with  the  streak  of  light  which  crosses  the  fusion 
area.  The  nearer  this  is  carried  by  a  rotary  prism,  or  a 
simple  prism,  base  out,  to  the  vertical  retinal  meridian, 
the  greater  would  be  the  demand  made  by  the  guiding 
sensation  on  the  center  controlling  the  external  rectus. 
For  this  reason  the  rod  test  will  give  variable  results 
from  time  to  time,  and  will  always  show  less  esophoria 
than  the  patient  really  has.  The  same  is  true  even  to  a 
greater  extent  when  the  rod  is  used  for  testing  for  exo- 
phoria  and  for  hyperphoria  and  cataphoria.  There  is 


ESOPHORIA.  291 

only  one  means  for  testing-  for  esophoria  that  is  less  reli- 
able than  the  rod,  and  that  is  the  strong-  plus  lens  sug- 
gested by  Stevens. 

From  every  standpoint  the  phorometer  constitutes  the 
most  desirable  means  for  detecting-  esophoria  and  meas- 
uring- it.  For  reasons  g-iven  in  Chapter  II.,  the  mo- 
nocular phorometer  is  the  best.  The  displacing-  prism 
should  always  be  placed,  base  up,  in  the  cell  toward  the 
patient's  eye;  the  thumbscrew  for  the  rotary  prism 
should  be  in  the  horizontal;  the  index  of  the  rotary 
prism  should  stand  at  zero;  and  the  spirit  level  should 
be  exactly  reg-ulated.  The  upper,  or  true,  object  should 
be  fixed.  The  six-degree  displacing-  prism  will  throw 
the  false  image  above  and  entirely  beyond  the  retinal 
area  of  binocular  fusion,  taking  the  guiding  sensation  of 
that  eye  entirely  off  its  guard,  so  that  the  eye  will  at 
once  be  turned  in.  The  lower,  or  false,  object  will  be 
proportionately  displaced  from  the  vertical  toward  the 
corresponding  side- — homonymous  diplopia.  Revolving 
the  rotary  prism  so  that  its  index  moves  in  the  nasal  arc, 
the  false  object  is  brought  farther  and  farther  toward 
the  vertical  line  passing  down  from  the  true  object,  un- 
til at  last  the  patient  observes  that  the  false  object  is  di- 
rectly under  the  true  object.  The  point  at  which  the 
index  stops  tells  the  degree  of  the  error.  The  same  re- 
sult, practically,  will  be  shown  by  any  number  of  tests 


292  ESOPHORIA. 

on  the  same  day  or  on  consecutive  days,  if  the  patient  is 
always  careful  to  "fix"  the  true  object.  This  point  is 
absolutely  essential  to  the  greatest  accuracy;  and  if 
strictly  observed,  there  is  no  other  factor  to  bring1  in  an 
error.  Certainly  at  no  time  will  the  false  imag'e  be 
within  the  retinal  area  of  binocular  fusion. 

The  one  eye  tested,  the  instrument  should  be  reversed 
so  as  to  test  the  other  eye,  for  in  this  way  only  can  it  be 
determined  if  there  is  more  esophoria  in  the  one  eye  than 
in  the  other. 

To  know  how  to  proceed  in  the  treatment  of  any 
grven  case,  this  question  must  be  answered:  Is  it 
pseudo-esophoria?  This  is  answered  by  a  study  of  the 
refraction  under  a  mydriatic  a  little  later.  If  there  is 
no  hyperopia  or  hyperopic  astigrnatism,  the  answer  is: 
"No."  If  there  is  hyperopia  or  hyperopic  astig-matism, 
the  answer  is,  "Yes,  at  least  in  part,"  which  part  can 
be  easily  calculated,  for  it  would  be  1.8°,  or  nearly  2°, 
for  every  dioptre  of  the  hyperopia  and  as  much  for  every 
2  D  of  hyperopic  astigfmatism.  The  quantity  of  the 
pseudo-esophoria  thus  determined,  subtracted  from  the 
full  error,  as  shown  by  the  phorometer,  gfives  the  amount 
of  the  true,  or  intrinsic,  esophoria. 

But  before  the  mydriatic  is  used  the  duction  and  ver- 
sion power  of  both  interni  and  both  externi  should  be 
taken  in  order  that  the  following*  two  questions  may 


ESOPHORIA.  203 

be  answered:  Is  the  intrinsic  esophoria  sthenic?  Is  it 
asthenic  ? 

These  three  questions  answered,  the  method  of  pro- 
cedure becomes  plain,  as  soon  as  complications  have  been 
found  or  eliminated. 

COMPLICATIONS  OF  ESOPHORIA. — These  are  hypero- 
pia  and  hyperopic  astigmatism,  hyperphoria  and  cata- 
phoria,  and  plus  and  minus  cyclophoria.  The  existence 
or  non-existence  of  one  or  more  of  these  complications 
must  be  known  before  it  becomes  possible  to  resort  to 
the  correct  treatment  of  esophoria.  It  has  already  been 
shown  how  hyperopia  and  hyperopic  astigmatism  develop 
a  pseudo-esophoria,  which  can  be  cured  by  proper  lenses. 
A  myopia  and  myopic  astigmatism  sometimes  compli- 
cate an  esophoria,  and  when  they  do,  their  correction  in- 
creases the  esophoria  in  the  near,  but  not  in  the  far. 

A  hyperphoria  of  one  eye  and  a  cataphoria  of  the 
other  will  increase  an  esophoria,  as  will  also  a  double 
hyperphoria  and  a  double  cataphoria.  How  to  deal  with 
these  complications  in  the  treatment  of  esophoria  will  be 
shown  under  the  head  "  Treatment." 

As  already  stated,  it  is  difficult  to  see  how  a  plus  or 
a  minus  cyclophoria  can  add  to  an  esophoria,  since  the 
oblique  muscles  are  abductors;  but  it  can  be  seen  readily 
how  an  esophoria  might  be  lessened  by  a  cyclophoria. 
It  is  possible,  however,  that  a  cyclophoria  may  excite 


294  ESOPHORIA. 

the  third  conjugate  innervation  center  in  some  way,  so 
as  to  develop  a  spasm  of  the  interni,  such  as  is  excited  in 
cases  of  hyperopia;  but  there  is  not  that  definite  rela- 
tionship between  the  obliques  and  the  interni  that  there 
is  between  the  ciliary  muscles  and  the  interni.  Never- 
theless, when  cyclophoria  complicates  an  esophoria,  the 
treatment  of  the  esophoria  must  include  the  treatment  of 
the  cyclophoria  if  the  best  and  quickest  results  are  to 
follow;  in  fact,  it  is  practically  impossible  to  cure  an 
esophoria  while  the  cyclophoria  remains  uncorrected. 

For  the  methods  of  detecting-  and  measuring-  hyper- 
phoria  and  cataphoria,  and  plus  and  minus  cyclophoria, 
as  complications  of  esophoria,  the  reader  is  referred  to 
Chapter  VI.  and  Chapter  VII. 

SYMPTOMS  OF  ESOPHORIA. 

These  are  any  one  or  several  of  those  mentioned  as 
resulting-  from  heterophoria,  and  the  reader  is  referred 
to  that  part  of  Chapter  III.  treating-  of  symptoms; 
but  not  all  the  symptoms  resulting-  from  abnormal 
nervous  tension  of  the  ocular  muscles  are  mentioned  in 
that  chapter.  It  would  be  impossible  to  make  a  com- 
plete list.  There  is  not  a  single  brain-center  controll- 
ing- any  one  organ  or  part  of  the  body  that  may  not  be  dis- 
turbed, in  sympathy  with  the  centers  that  control  the 
ocular  muscles;  and,.wc<?  versa,  the  centers  controlling 


ESOPHORIA.  295 

the  ocular  muscles  may  be  sympathetically  disturbed 
because  of  excessive  demands  on  the  other  centers.  The 
difference  between  other  centers  and  those  controlling 
the  ocular  muscles  is  that  the  former  have  not  so  severe 
a  taskmaster  as  the  guiding-  sensation  which  compels 
obedience,  on  the  part  of  the  ocular  muscles,  to  the  law 
of  corresponding  retinal  points  in  binocular  vision.  For 
this  reason  no  other  centers  are  so  likely  to  be  over- 
worked as  are  the  eight  fusional  innervation-centers 
whose  duty  is  to  control  the  recti  muscles  so  that  the 
visual  axes  may  always  be  in  the  same  plane  and  may  be 
converged  at  the  proper  point,  and  the  four  conjugate 
centers  that  force  the  obliques  to  parallel  the  vertical 
axes  with  the  median  plane  of  the  head.  The  only  ex- 
ception is  the  center  that  controls  the  action  of  the  ciliary 
muscles,  which  must  also  satisfy  the  guiding  sensation 
of  the  retina. 

In  monocular  vision,  as  when  one  eye  has  been  lost, 
the  possibility  of  the  excitation  of  reflex  nervous  symp- 
toms is  greatly  lessened.  The  centers  not  relieved  of 
the  necessity  of  over-excitation  when  there  is  but  one 
eye  are  the  center  that  sends  impulses  to  the  ciliary 
muscle  and  the  centers  that  must  make  the  obliques 
parallel  the  vertical  axis  with  the  median  plane  of  the 
head.  Posing  the  head  in  monocular  vision  would  re- 
lieve the  strain  that  may  have  been  demanded  of  the 


296  ESOPHORIA. 

recti  in  binocular  vision.  There  is,  therefore,  truth  in 
the  statement  that  has  been  made  by  people  who  have 
lost  one  eye — that  ' '  the  one  eye  is  stronger  than  the  two 
ever  were." 

The  symptoms  of  esophoria  are  not  due  directly  to  the 
abnormally  high  inherent  tension  of  the  interni,  but  to 
the  abnormal  nervous  tension  of  the  externi  in  their 
effort  to  prevent  the  esophoria  from  being1  transformed 
into  an  esotropia,  or  to  the  nervous  tension  of  other  weak 
muscles  in  their  effort  to  counteract  other  errors  that 
may  complicate  the  esophoria. 

TREATMENT  OF  ESOPHORIA. 

Errors  of  refraction  that  complicate  an  esophoria 
should  be  measured  under  a  mydriatic,  and  a  full  correc- 
tion should  be  given.  If  the  error  is  hyperopia,  every 
dioptre  of  correction  will  relieve  1.8°,  practically  2°,  of 
the  esophoria  both  in  the  far  and  in  the  near;  if  the  error 
is  hyperopic  astigmatism,  every  dioptre  of  correction  will 
relieve  0.9°,  practically  1°,  of  the  esophoria.  The  pseudo- 
esophoria  is  thus  cured.  Any  remaining  esophoria  is 
intrinsic  in  character,  unless  it  be  caused  by  subnormally 
developed  ciliary  muscles,  which  would  be  shown  in  the 
near  only. 

If  the  refractive  error  is  myopia,  every  dioptre  of  cor- 
rection will  add  to  the  manifest  esophoria — in  the  near, 


ESOPHORIA.  297 

but  not  in  the  far— 1.8°,  that  quantity  of  pseudo-exo- 
phoria  which,  before  correction,  served  to  lessen  the  eso- 
phoria;  if  the  error  be  myopic  astigmatism,  every  dioptre 
of  correction  would  add  0.9°  to  the  formerly  manifest 
esophoria,  but  in  the  near  only.  With  the  correcting 
lenses  on,  the  esophoria  shown  by  the  phorometer  is  in- 
trinsic in  character. 

Thus  it  is  shown  that  the  correction  of  hyperopia 
and  hyperopic  astigmatism  lessens  the  nervous  tension 
of  the  externi  by  relieving  the  associated  nervous  tension 
of  both  the  interni  and  the  externi;  while  in  intrinsic 
esophoria  the  nervous  tension  is  in  the  externi  alone,  the 
tension  of  the  interni  being  inherent.  To  obtain  full 
correction  of  the  pseudo-esophoria,  the  hyperopia  and 
the  hyperopic  astigmatism  should  be  fully  corrected, 
and  the  correction  must  be  worn  both  for  near  and  for 
far  seeing.  If  the  esophoria  is  wholly  pseudo,  noth- 
ing will  be  needed  but  the  lenses  for  effecting  a  com- 
plete cure;  but  if  a  part  of  the  esophoria  is  intrinsic, 
as  may  always  be  known  without  waiting,  other  treat- 
ment will  be  necessary  sooner  or  later.  The  double 
nervous  tension  having  been  relieved  by  the  lenses,  all 
symptoms  may  vanish  for  a  time  ;  but  ultimately  the 
nervous  tension  of  the  externi,  necessary  for  correcting 
the  intrinsic  esophoria,  will  cause  symptoms  to  reappear. 
This  marked  relief  will  follow  only  when  the  intrinsic 


298  ESOPHORIA. 

esophoria  is  low  in  degree,  while  the  pseudo-esophoria 
is  comparatively  hig-h. 

The  wearing-  of  lenses  correcting-  myopia  and  myopic 
astigmatism  will  cause  no  chang-e  in  the  muscle  imbal- 
ance for  distance  ;  but  in  the  near,  the  wearing-  of  the 
lenses  will  cause  the  whole  of  the  esophoria  to  become 
manifest,  and  the  nervous  tension  of  the  externi  will 
be  correspondingly  augmented;  the  symptoms  will  be 
aggravated,  and  the  esophoria  should  receive  immedi- 
ate treatment.  Until  the  esophoria  has  been  cured  it 
will  be  better  to  let  the  patient  take  the  lenses  off  when 
engaging  in  near  work,  or,  at  most,  wear  only  a  partial 
correction  of  the  myopic  error.  Uncorrected  myopia 
lessens  the  nervous  tension  of  the  externi  in  esophoria 
by  diminishing  the  normal  nervous  impulse  that  would 
be  sent  to  the  interni,  if  the  ciliary  muscles  were  in 
action. 

The  effect  of  focal  errors  eliminated,  the  treatment  of 
the  intrinsic  esophoria  depends  on  the  quantity  of  the 
error,  in  so  far  as  non-operative  efforts  are  concerned. 

The  non-operative  treatment  of  esophoria  of  low 
degree  is  of  two  kinds  —  first,  prisms  in  position  of 
action  for  the  stronger  muscles  or  of  rest  for  the 
weaker  muscles;  second,  exercise  of  the  weaker  mus- 
cles, which,  in  cases  of  esophoria,  can  be  accomplished 
only  by  prisms. 


ESOPHORIA.  299 

PRISMS  IN  POSITIONS  OF  ACTION  FOR  THE 
INTERNI. 

Prisms  to  be  worn  constantly  are  always  open  to  the 
objection  that  they  interfere  with  the  law  of  direction, 
but  this  is  sometimes  the  less  of  two  evils  and  should  be 
chosen.  The  visual  axis  under  any  and  all  circumstances 
points  to  the  apparent  source  of  the  light  that  throws 
its  image  on  the  macula.  In  obedience  to  the  law  of  cor- 
responding- retinal  points,  an  image  that  has  been  dis- 
placed, by  prismatic  action,  toward  the  temporal  side 
of  the  macula,  makes  the  source  of  the  light  appear  to  be 
on  the  opposite  side  and  just  as  man}r  degrees  from  its 
real  position  as  the  image  has  been  displaced  from  the 
macula.  When  possible,  fusion  of  the  false  object  with 
the  true  object  is  effected  by  the  internus  rotating  the 
eye  until  the  macula  is  brought  under  the  displaced  im- 
age. The  visual  axis  points  to  where  the  object  would 
appear  to  be  if  no  attempt  at  fusion  had  been  made,  and 
of  necessity  passes  through  the  center  of  retinal  curva- 
ture. The  visual  line  that  passes  from  the  displaced  im- 
age to  the  fused  object  passes  to  the  outer  side  of  the 
center  of  the  retinal  curve,  and  is  a  false  line  of  direction. 

Before  placing  a  prism  for  constant  wear  by  an  eso- 
phoric,  the  complicating  muscle  errors  must  be  consid- 
ered. The  only  indication  for  placing  the  axis  of  the 
prism  out  of  the  horizontal  is  the  coexistence  of  a  cyclo- 


300  ESOPHORIA. 

phoria,  usually  a  plus  cyclophoria,  either  with  or  with- 
out a  complicating  hyperphoria  of  the  one  eye  and  a  cata- 
phoria  of  the  other.  If  there  is  no  vertical  error,  but 
only  a  plus  cyclophoria  complicating-  the  esophoria,  the 
prismatic  effect  should  be  divided  equally  between  the 
two  eyes,  and  the  nasal  end  of  each  axis  should  be  tilted 
up  through  a  sufficient  arc  for  correcting  the  greater  part 
of  the  cyclophoria.  This  must  be  determined  by  test- 
ing for  the  cyclophoria  while  the  prisms  are  on.  The 
stronger  the  prisms,  the  smaller  the  arc  of  rotation  of 
the  axes;  and,  vice  versa,  the  weaker  the  prisms,  the 
larger  the  arc  of  rotation.  To  place  the  prisms,  in  such  a 
case,  with  the  axes  horizontal,  would  be  to  leave  uncor- 
rected  the  cyclophoria,  a  most  important  factor  in  the 
causation  of  symptoms.  To  depress  the  nasal  end  of  the 
axes  of  the  prisms,  in  a  case  of  this  kind,  would  be  to 
make  the  patient  worse. 

If  there  is  a  complicating  hyperphoria  of  one  eye  and 
cataphoria  of  the  other  eye,  as  well  as  a  complicating 
plus  cyclophoria,  the  prismatic  effect  for  the  relief  of 
the  esophoria  should  be  applied  wholly  or  in  greater 
part  to  the  eye  that  is  hyerphoric  and  the  nasal  end  of 
the  axis  should  be  elevated.  As  can  be  readily  seen,  a 
prism  thus  placed  would  cause  the  eye  to  turn  in  and  up, 
the  direction  the  strong  muscles  tend  to  take  it,  which 
rotation  wrould  tort  the  eye  in,  correcting  the  plus  cyclo- 


ESOPHORIA.  301 

phoria.  If  any  of  the  prismatic  effect  is  applied  to  the 
cataphoric  eye,  the  axis  should  be  horizontal,  for  the  rea- 
son that,  while  depressing-  the  axis  of  the  prism  would 
rest  the  weak  superior  rectus,  it  would  increase  the  plus 
cyclophoria;  on  the  other  hand,  elevating  the  nasal  end 
of  the  axis  \vould  favor  the  weak  superior  oblique,  but 
would  add  to  the  abnormal  nervous  tension  of  the  weak 
superior  rectus. 

In  a  case  of  esophoria,  complicated  with  a  minus  cy- 
clophoria, the  rule  for  tilting1  the  axes  of  the  prisms 
would  be  reversed  all  the  way  through.  This  compli- 
cation is  exceedingly  rare. 

If  the  esophoria  is  uncomplicated  in  a  given  case,  the 
prismatic  effect  should  be  equally  divided  between  the 
two  eyes.  These  prisms  can  be  worn  with  comfort,  pro- 
vided the  two  intern!  are  properly  attached,  and  in  many 
cases  they  can  be  worn  comfortably  if  the  two  interni 
are  attached,  in  greater  part,  above  the  horizontal  plane 
of  the  eyes.  In  many  cases  the  superior  obliques  would 
accept  kindly  the  aid,  in  paralleling  the  vertical  axes 
with  the  median  plane  of  the  head,  offered  by  the 
interni  that  are  attached  too  high.  Constant  prisms 
for  esophoria,  when  uncomfortable,  point  to  attach- 
ments of  the  interni  that  are,  in  greater  part,  below 
the  horizontal  plane.  In  such  a  case  the  prisms 
would  have  to  be  abandoned.  The  combined  prismatic 


302  ESOPHORIA. 

effect,  as  a  rule,  should  not  be  more  than  half  the  eso- 
phoria. 

When  focal  errors  require  either  convex  or  concave 
lenses,  these  can  be  decentered  so  as  to  give  the  necessa- 
ry prismatic  effect.  Por  esophoria,  convex  lenses  should 
be  decentered  out  and  concave  lenses  should  be  decen- 
tered in.  The  same  rules  for  placing-  prisms  should 
govern  the  decentering  of  lenses.  It  would  seem 
that  authors  ought  to  agree  as  to  how  much  a  given 
lens  should  be  decentered  in  order  to  obtain  a  definite 
prismatic  effect,  but  they  do  not.  Maddox  teaches  that 
a  lens  of  1  D  must  be  decentered  1.75  cm.  (17  5  mm.)  to 
obtain  1°  of  prismatic  effect.  He  then  gives  the  follow- 
ing formula  for  determining  the  extent  of  decentration 
of  any  lens  for  a  required  effect:  C  =  P>^>  in  which  C  is 
the  centimeters  of  decentering;  P,  the  desired  prismatic 
effect;  and  D,  the  number  of  dioptres  in  the  lens.  Let 
P  =  lij0  and  D  =  3°,  then  the  formula  w^ould  be: 
C  =  1H ^ 13^  =  .875  cm.,  or  8.75  mm.,  which  is  about  ^  of 
an  inch  of  decentering. 

Jackson  teaches  that  the  following  formula  is  practi- 
cally correct :  C  =  ^—,  in  which  C  is  the  mm.  of  decen- 
tering required;  P,  the  prismatic  effect  desired;  D,  the 
number  of  dioptres  in  the  lens  to  be  decentered;  while  10 
is  the  mm.  of  decentering  of  a  1  D  lens  for  1°  (1  centrad) 
of  effect.  Substituting  figures  for  letters,  as  in  the 


SSOPHORIA.  303 

Maddox  formula,  we  have  :  C  =  ULf£==  5  mm>>  or  about 
B  of  an  inch  of  decentering,  as  compared  with  Maddox's 
•J-  of  an  inch  of  decentering. 

Thorington  and  May  agree  in  taking  8.7  mm.  for  the 
extent  of  decentering  a  1  D  lens  in  order  to  procure  1° 
of  prismatic  effect.  For  obtaining  the  amount  of  de- 
centration  of  any  lens,  this  would  be  their  formula: 
C  =  P$r?.  Substituting  figures  for  letters,  as  in  the 
other  formulas,  we  have:  C  ==  l%->pl  ==  4.35  mm.?  or 
about  i  of  an  inch  of  decentration,  as  compared  with 
Maddox's  |  of  an  inch  and  Jackson's  »  of  an  inch  ;  or, 
comparing  in  mm.:  Maddox,  8.7;  Jackson,  5;  Thoring- 
ton,  4.35;  May,  4.35.  By  a  little  experimentation  the 
reader  may  satisfy  himself  that  Jackson  is  practically 
correct.  The  extent  of  decentration  advised  by  Maddox 
is  entirely  too  much — nearly  double  what  it  ought  to  be. 
It  may  be  that  Maddox's  estimate  was  for  1°  of  arc,  and 
not  for  1°  of  prism,  or  1  centrad. 

One  advantage  that  decentering  a  lens  has  over  the 
grinding  of  a  lens  on  a  prism  is  that  the  former  is 
cheaper ;  another  advantage  is  that  the  wearing  of  a 
decentered  lens  is  not  attended  by  the  reflected  image  of 
any  bright  object,  which  is  always  toward  the  refract- 
ing angle  and  in  the  line  of  the  axis  of  the  prism,  unless 
the  prism  is  ground  on  both  surfaces.  Chromatic  aber- 
ration is  no  more,  nor  is  it  anv  less,  with  a  decentered 


304  ESOPHORIA. 

lens  than  it  is  with  a  lens  ground  on  a  prism.  The 
great  objection  to  decentered  lenses  is  that  the  spherical 
aberration  must  interfere  to  some  extent  \vith  the  sharp- 
ness of  retinal  images;  this,  however,  is  but  little  when 
the  decentering  is  6  mm.  or  less,  and  rarely  is  it  more. 
In  very  strong  lenses,  say  6  D,  the  decentering  would 
be  only  5  mm.  for  3°  of  effect. 

The  greatest  objection  to  "relieving  prisms"  and  to 
decentered  lenses  is  that  they  favor  muscles  in  their 
weakness.  They  lessen  nervous  tension,  but  not  by 
increasing  the  inherent  power  of  weak  muscles.  It  is 
far  better  practice  to  increase  the  inherent  power  of 
weak  muscles,  either  by  exercising  them  or  by  shorten- 
ing or  advancing  them,  or  to  increase  the  relative  power 
of  the  weaker  muscles  by  lessening  the  tension  of  their 
stronger  antagonists  by  partial  tenotomies.  If  patients 
will  not  resort  to  exercise  and  decline  to  submit  to 
operations,  they  should  be  given  the  benefit  which  is  to 
be  derived  from  prisms  in  positions  of  rest  or  from  de- 
centered  lenses. 

EXERCISE   TREATMENT  FOR    ESOPHORIA. 

Uncomplicated  intrinsic  esophoria  of  low  degree  may  be 
cured  by  proper  exercise  of  the  externi.  The  only  means 
applicable  are  prisms.  The  same  gymnastic  principles 
apply  to  the  externi  as  to  the  other  muscles  of  the  body. 


ESOPHORIA.  305 

Light  work,  not  continued  too  long,  and  rhythmic  in 
character,  is  exercise  that  increases  muscular  power. 
Prisms  of  from  1°  to  4°,  bases  in,  can  be  used  for  devel- 
oping- the  externi.  Beginning-  with  the  weaker  prisms 
and  advancing  to  the  next  stronger  at  intervals  of  a 
week  or  ten  days,  the  strongest  to  be  used  are  soon 
reached.  The  exercise  should  be  resorted  to  at  the  same 
time  every  day,  so  as  to  easily  form  the  habit  of  exer- 
cising, and  should  be  continued  not  longer  than  ten  min- 
utes at  a  time.  One  exercise  daily — or,  at  most,  two  ex- 
ercises daily — will  be  sufficient.  I/enses  correcting  focal 
errors  should  be  worn  at  the  time  of  exercising.  The 
exercise  prisms  in  spectacle  frames  should  be  lowered 
and  raised  alternately  every  three  seconds  throughout 
the  sitting.  The  object  looked  at  may  be  anything  that 
can  be  seen  distinctly,  and  it  should  be  distant  from  the 
observer  not  more  than  twenty  feet  nor  less  than  ten 
feet.  Looking  at  the  object  through  the  prisms,  the 
externi  are  made  to  contract;  raising  the  prisms,  these 
muscles  at  once  relax.  Thus  contraction  and  relaxation, 
rhythmic  in  character,  are  continued  throughout  the  sit- 
ting. Exercise  that  fatigues  does  not  build,  hence  the 
necessity  of  always  stopping  short  of  fatigue.  A  muscle 
develops  as  the  result  of  exercise  in  proportion  to  the 
abundance  of  blood  that  can  be  brought  into  it.  Abund- 
ance of  blood  supply  means  quick  results;  scanty  blood 


306  ESOPHORIA. 

supply,  because  of  smallness  of  the  vessels  supplying 
the  muscle,  means  slow  results.  These  conditions  can- 
not be  known  beforehand;  therefore  it  is  better  to  tell 
the  patient  that  the  treatment  will  have  to  be  continued 
for  months. 

Exercise  of  the  externi  that  are  attached,  in  greater 
part,  below  the  horizontal  plane,  will  exercise,  at  the 
same  time,  the  inferior  obliques,  which  would  be  good 
in  a  case  of  minus  cyclophoria,  but  bad  in  a  case  of  plus 
cyclophoria.  If  the  externi  have  the  ideal  attachment — 
that  is,  half  above  and  half  below  the  transverse  plane  of 
the  eye — exercise  will  always  be  well  borne  and  will  do 
good.  If  attached  too  high,  the  exercise  of  the  externi 
will  be  associated  with  exercise  of  the  superior  obliques 
and  will  usually  be  well  borne  and  ought  to  do  good. 
These  things  can  be  known  only  as  a  result  of  exercise. 

The  object  in  view  in  exercising  the  externi  is  to  so 
increase  their  inherent  power  that,  under  a  normal  im- 
pulse, they  will  be  able  to  do  a  normal  amount  of  work; 
that  their  tension  may  be  inherent,  not  nervous,  and 
sufficient  to  balance  the  inherent  tension  of  the  interni. 

OPERATIONS. 

No  operation  for  pseudo-esophoria  should  ever  be  done. 
The  kind  depending  on  hyperopia  should  be  treated  by  a 
full  correction  of  the  focal  error;  the  kind  due  to  subnor 


ESOPHORIA.  307 

mal  development  of  the  ciliary  muscles,  making  it  neces- 
sary that  the  center  controlling  them  shall  generate  an 
extraordinary  nerve  impulse,  should  be  treated  by  gym- 
nastic exercise  of  these  muscles. 

There  can  be  drawn  no  unvarying  line  between  opera- 
tive and  non-operative  cases  of  intrinsic  esophoria.  If, 
under  the  red-glass  test,  there  is  homonymous  diplopia, 
the  case  is  almost  certainly  one  to  be  operated  upon;  but 
the  kind  of  operation  is  not  shown  by  this  test.  If  the 
esophoria  at  16  inches  is  more  than  half  the  angle  of  con- 
vergence (nearly  9°)  for  that  distance,  the  question  of 
operation  should  be  considered;  and  if  it  is  much  in  excess 
of  5°  in  the  near,  there  is  no  reason  why  an  operation 
should  be  delayed.  Whatever  the  quantity  of  esophoria  in 
the  distance,  which  is  usually  a  little  greater  than  that 
in  the  near,  it  should  not  be  relied  on  exclusively  when  de- 
termining on  an  operation.  Both  the  near  and  the  far 
tests  should  always  be  noted.  The  quantity  of  error  be- 
ing sufficiently  great  to  indicate  an  operation,  the  next 
thing  to  consider  is  the  question  as  to  whether  the  eso- 
phoria is  sthenic  or  asthenic.  More  than  25°  of  adduc- 
tion and  more  than  50°  of  adversion  would  indicate  a  par- 
tial tenotomy  of  one  or  both  interni;  there  is  nothing  in 
esophoria  that  can  justify  a  complete  tenotomy.  If  the 
adduction  is  25°  or  less  and  the  adversion  is  50°  or  less, 
no  operation  should  be  done  on  the  interni,  but  one  or 


308  ESOPHORIA. 

both  extern!  should  be  shortened.  If  in  doubt  as  to 
which  of  the  two  operations  should  be  done,  it  would  be 
safer  to  choose  the  shortening-  of  an  externus.  Either 
operation  would  cure  wholly  or  in  part  the  imbalance — 
the  partial  tenotomy,  by  lessening1  the  tension  of  the  in- 
ternus;  the  shortening-,  by  increasing  the  tension  of  the 
externus.  In  properly  selected  cases  either  operation 
would  establish  a  sthenic  orthophoria;  in  unfortunately 
selected  cases  (those  with  normal  or  subnormal  adduc- 
tion) the  tenotomy  would  establish  an  asthenic  orthopho- 
ria, a  danger  never  attending  the  operation  of  shortening. 

Abduction  in  an  operable  case  of  esophoria  is  a  safe 
guide  in  determining  whether  the  operation  should  be 
done  to  lessen  the  tension  of  an  internus  or  to  increase 
the  tension  of  an  externus.  If  the  abduction  is  above  5° 
or  6°  and  the  abversion  is  but  little  below  50°,  the  inter- 
nus should  be  cut;  if  abduction  is  below  5°  and  abver- 
sion is  correspondingly  low,  the  externus  should  be 
shortened. 

In  uncomplicated  cases  of  esophoria,  the  error  about 
equal  in  the  two  eyes,  the  operative  effect  should  be  di- 
vided between  them.  In  such  cases  the  plane  of  rotation 
must  not  be  altered,  hence  the  partial  tenotomy  must  be 
central  and  the  shortening  must  be  straight  forward. 

When  esophoria  is  complicated  with  only  hyperphoria 
of  one  eye  and  cataphoria  of  the  other,  the  operations  on 


ESOPHORIA.  309 

the  lateral  muscles  should  be  done  as  if  there  were  no 
complications — that  is,  the  tension  of  the  muscles  should 
be  altered,  but  their  planes  should  not  be  changed. 

•*•  o 

Later  the  hyperphoria  should  be  treated  either  by  a  per- 
manent prism  for  the  hyperphoric  eye,  by  prismatic  exer- 
cise of  the  weaker  muscle  of  each  eye,  or  by  a  central 
partial  tenotomy  of  the  superior  rectus  of  the  hyper- 
phoric eye. 

When  esophoria  is  complicated  by  cyclophoria  alone 
or  by  cyclophoria  and  hyperphoria,  the  operation  done 
must  not  only  alter  the  tension  of  the  muscle,  but  must 
also  change  its  plane  of  rotation.  If  the  complication  is 
plus  cyclophoria  alone  and  the  operation  is  to  lessen  the 
tension  of  the  internus,  it  should  be  so  done  as  to  ele- 
vate its  plane  of  rotation.  Th:s  is  accomplished  by  a 
lower  marginal  tenotomy,  leaving  uncut  the  fibers  at 
the  upper  margin.  A  threefold  effect  attends  this  oper- 
ation: (a)  the  tension  is  lessened,  (b)  the  cyclophoria  is 
counteracted,  (c)  a  hyperphoria  is  created.  For  the  rea- 
son that  an  operation  on  only  one  internus  would  give  a 
hyperphoria  to  the  corresponding  eye,  the  operative  ef- 
fect should  be  divided  between  the  two  eyes,  the  opera- 
tion on  the  one  internus  being  as  nearly  as  possible  like 
the  operation  on  the  other.  The  two  operations  should 
cure  the  esophoria  and  the  plus  cyclophoria;  but  at  the 
same  time  a  double  hyperphoria  would  be  created,  a  con- 


310  ESOPHORIA. 

dition  far  less  objectionable  than  the  two  errors  for  the 
cure  of  which  the  operations  were  done. 

If  the  sthenic  esophoria  is  complicated  by  plus  cyclo- 
phoria,  with  hyperphoria  and  cataphoria,  the  operative 
effect  should  be  confined,  if  possible,  to  the  internus  of 
the  cataphoric  eye  and  should  consist  of  a  division  of  the 
lower  and  central  fibers,  leaving1  uncut  enough  of  the 
upper  fibers  to  prevent  an  over-effect.  The  result  of 
this  operation  would  be  threefold:  (a)  lessening-  or  cur- 
ing- the  esophoria;  (b)  counteracting-  the  plus  cyclophoria; 
(c)  converting-  the  cataphoria  into  a  hyperphoria,  thus 
giving-  the  patient  a  double  hyperphoria.  If  some  of  the 
esophoria  should  remain,  it  should  be  relieved  by  a  cen- 
tral partial  tenotomy  of  the  internus  of  the  other  eye.  A 
marginal  tenotomy  of  this  muscle  should  not  be  done,  even 
if  some  of  the  plus  cyclophoria  and  hyperphoria  remained, 
for  the  reason  that  dividing-  its  lower  fibers  would  in- 
crease the  hyperphoria  while  curing  the  cyclophoria. 
How  to  deal  with  any  remaining-  cyclophoria  and  hyper- 
phoria will  be  shown  in  the  discussion  of  those  conditions. 

If  the  esophoria  is  asthenic  and  uncomplicated,  one  of 
the  externi,  if  not  both,  should  be  shortened  so  as  to  in- 
crease its  tension  without  changing  its  plane  of  action. 
If  complicated  by  a  hyperphoria  of  one  eye  and  a  cat- 
aphoria of  the  other,  there  being-  no  cyclophoria,  the 
shortening  of  the  externi  should  be  done  as  if  no  compli- 


ESOPHORIA.  311 

cation  existed;  that  is,  the  tension  should  be  increased, 
but  the  plane  should  not  be  changed.  If  complicated  by 
a  plus  cyclophoria  only,  both  externi  should  be  shortened 
to  the  same  extent  and  the  plane  of  each  should  be  low- 
ered sufficiently  to  effect  a  correction  of  the  cyclophoria. 
The  alteration  of  the  tension  would  cure  the  esophoria. 
If  the  complications  are  plus  cyclophoria  and  a  hyper- 
phoria  of  one  eye  and  a  cataphoria  of  the  other,  the  oper- 
ative effect,  if  possible,  should  be  limited  to  the  hyper- 
phoric  eye,  and  should  be  accomplished  by  a  shortening 
of  the  externus  so  as  both  to  alter  its  tension  and  to  de- 
press its  plane  of  action.  The  triple  effect  would  be: 
(a)  increased  tension  for  the  esophoria;  (b)  lowered  plane 
for  the  plus  cyclophoria;  (c)  lowered  plane  for  the  hyper- 
phoria,  converting  it  into  a  cataphoria,  so  that  there 
would  be  a  double  cataphoria.  If  any  remaining  esopho- 
ria should  require  a  shortening  of  the  externus  of  the 
other  eye,  the  operation  should  be  done  so  as  to  increase 
its  tension  without  changing  its  plane,  even  if  there 
should  also  remain,  from  the  first  operation,  some  of  the 
plus  cyclophoria  and  some  of  the  cataphoria;  for  a  change 
of  the  plane  of  action  that  would  lessen  one  of  these 
complications  would  increase  the  other. 

The  complication  of  minus  cyclophoria  has  only  been 
mentioned,  for  the  reason  that  it  is  so  rare.  When  it 
does  exist  in  connection  with  esophoria,  every  step  for 


312  ESOPHORIA. 

changing-  the  muscle  plane,  as  set  forth  in  the  treatment 
of  a  plus  cyclophoria,  must  be  reversed. 

The  operation  of  shortening-  an  externus,  when  enough 
increase  of  tension  can  be  had,  should  always  be  pre- 
ferred to  an  advancement.  While  this  can  be  done  in 
nearly  all  cases  of  asthenic  esophoria,  in  which  an  in* 
crease  of  tension  of  the  externi  is  always  indicated, 
nevertheless,  in  some  cases  these  muscles  have  their  at- 
tachment so  far  removed  from  the  corneo-scleral  junc- 
tion that  the  advancement  operation  becomes  clearly  in- 
dicated. The  same  rules  as  to  alteration  of  tension  and 
chang-e  of  plane  apply  to  advancements  as  have  been  set 
forth  in  connection  with  shortening's.  For  the  technic 
of  these  operations,  and  the  after-treatment,  the  reader 
is  referred  to  that  part  of  Chapter  III.  in  which  these 
operations  are  described. 

While  doing1  these  operations  the  judg-ment  of  the 
operator  must  decide  as  to  their  extent.  His  judgment 
cannot  be  g^ood  unless  he  keeps  in  mind  the  exact  nature 
of  the  conditions  for  the  relief  of  which  he  is  operating". 
The  true  essence  of  these  conditions  cannot  be  known 
except  as  a  result  of  the  most  skillful  and  careful  use  of 
the  phorometer,  cyclo-phorometer,  and  tropometer  or 
perimeter.  Before  any  operation  is  done,  the  refraction 
of  the  eyes  should  be  determined,  under  a  mydriatic,  by 
means  of  the  standard  objective  and  subjective  tests. 


ESOPHORIA.  313 

The  operator  should  always  be  careful  not  to  do  too 
much;  for  it  is  far  better  to  leave  the  patient  with  some 
of  his  esophoria  than  it  is  to  give  him  the  smallest  quan- 
tity of  the  opposite  error — exophoria.  The  danger  of  re- 
sorting to  tests  while  operating  is  that  it  may  lead  to 
the  doing  of  too  much.  Tests  while  operating  cannot 
be  reliable,  and  should,  therefore,  be  avoided.  When 
more  than  one  operation  is  needed,  it  is  better  to  allow 
from  two  to  four  weeks  to  intervene;  but  in  errors  of 
high  degree,  two  operations,  a  partial  tenotomy  of  an  in- 
ternus  and  a  shortening  of  the  opposing  externus,  or  a 
partial  tenotomy  of  both  interni,  or  a  shortening  of  both 
externi,  may  be  done  at  the  same  time. 

The  object  of  partial  tenotomies  of  the  interni,  in 
the  treatment  of  esophoria,  is  to  so  reduce  their  tension 
that  the  externi,  under  a  normal  impulse,  may  perfectly 
balance  them  in  action.  The  object  of  shortening  the 
externi  is  to  so  increase  their  inherent  tension  that, 
under  a  normal  impulse,  they  may  perfectly  balance  the 
interni.  In  either  case  the  nervous  tension  of  the  ex- 
terni would  be  relieved. 

Whenever  an  intrinsic  esophoria  has  been  reduced  by 
operations  so  that  the  remainder  can  be  cured  by  non- 
operative  means,  these  should  be  resorted  to,  but  not 
until  the  muscles  operated  upon  have  had  time  to  com- 
pletely recover  from  the  operations. 


CHAPTER  V. 


EXOPHORIA. 


As  the  word  indicates,  there  is,  in  exophoria,  a  ten- 
dency on  the  part  of  the  external  recti  muscles  and  their 
synergists  to  make  the  visual  axes  deviate  from  the  point 
of  fixation.  If  this  tendency  were  not  counteracted  by 
antagonists  of  the  externi,  the  visual  axes  would  either 
intersect  beyond  the  point  of  fixation,  or  they  would 
become  parallel  or  even  divergent.  Abnormal  nervous 
tension  of  the  interni  and  their  synergists  counteracts 
the  inherent  tension  of  the  externi  and  their  synergists, 
so  that  the  tendency  is  not  allowed  to  become  a  turning. 
The  visual  axes  are  thus  forced  to  intersect  at  the  point 
of  fixation;  and  binocular  single  vision  is  maintained,  but 
at  the  expenditure  of  an  undue  amount  of  nerve  force. 
Exophoria,  like  esophoria,  is  of  two  kinds,  intrinsic  and 
pseudo.  As  to  causation,  the  one  kind  is  wholly  different 
from  the  other,  but  the  two  often  coexist.  As  to  the 
results,  the  one  is  the  same  in  kind  as  the  other,  but 
the  treatment  of  the  one  is  not  at  all  similar  to  the  treat- 
ment of  the  other. 

(314) 


EXOPHORIA.  315 

INTRINSIC  EXOPHORIA.— In  this  the  extern!  have  the 
advantage  over  the  interni.  This  imbalance  may  be  due 
to  the  fact  that  the  externi  are  hyper-developed  or  that 
the  interni  are  of  subnormal  development.  It  may  be 
that  the  error  is  not  in  the  size  of  the  muscles,  but  in  the 
nature  of  their  attachment  to  the  globe,  the  externi  hav- 
ing their  attachment  nearer  the  corneo-scleral  junction 
than  normal,  or  that  the  interni  are  attached  too  far 
back;  it  may  be  that  the  externi  are  short  and  tense  or 
that  the  interni  are  long  and  somewhat  lax.  When  either 
of  these  conditions  causes  exophoria,  the  error  may  be 
greater  in  the  one  eye  than  in  the  other,  though,  as  a 
rule,  the  exophoria  is  about  equal  in  the  two  eyes.  When 
there  is  a  difference,  the  monocular  phorometer  quickly 
shows  it. 

It  must  be  conceded  that  the  cause  of  intrinsic  exopho- 
ria may  not  reside  in  the  muscles  themselves,  but  may 
be  found  in  an  unequal  supply  of  nerve  force,  the  centers 
for  the  externi  generating  a  quantity  of  nerve  impulse 
greater  than  normal,  or  the  third  conjugate  brain-center, 
of  subnormal  development,  sending  a  weaker  current  to 
the  interni. 

An  intrinsic  exophoria  can  exist  without  there  being 
a  state  of  imbalance  between  the  externi  and  the  interni. 
The  oblique  muscles  are  always  more  or  less  powerful  as 
abvertors.  There  is  but  little  room  for  doubt  that,  in 


316  EXOPHORIA. 

some  cases,  they  may  be  too  short  and  tense,  or  they  may 
be  too  large  and  powerful,  or  their  attachments  may  be 
nearer  the  posterior  pole  than  normal,  so  that,  in  either 
case,  their  abverting  power  would  be  increased.  This 
increase  may  be  sufficiently  great  to  cause  an  exophoria, 
even  when  there  is  no  cyclophoria. 

Malformation  of  the  orbits,  only  in  the  sense  of  their 
being  too  far  apart,  can  cause  an  exophoria;  but  when 
this  cause  exists  alone,  the  muscle  imbalance  cannot  be 
great. 

The  superior  and  inferior  recti  may  have  their  attach- 
ments so  far  toward  the  temples  as  to  greatly  lessen 
their  power  to  help  the  interni,  and  thus  become  a  factor 
in  the  production  of  exophoria. 

Whether  the  one  or  the  other  of  the  several  conditions 
named  is  the  cause  of  exophoria,  or  whether  two  or  more 
of  them  become  factors  in  the  production  of  this  error, 
the  treatment,  whether  surgical  or  non-surgical,  must  be 
directed  toward  the  lateral  muscles.  As  to  surgical 
means,  either  the  tension  of  the  externi  must  be  lessened 
or  the  tension  of  the  interni  must  be  increased.  If  brain- 
centers  are  structurally  over-developed  or  under-devel- 
oped, they  must  remain  so  always;  if  the  obliques,  be- 
cause of  structure,  attachment,  or  innervation,  abvert 
too  powerfully,  they  cannot  be  changed;  if  the  orbits 
are  too  wide  apart,  surgery  cannot  bring  them  closer  to- 


EXOPHORIA.  317 

gether.  If  the  superior  and  inferior  recti,  because  of 
faulty  attachments,  are  feeble  advertors,  they  must  not 
be  subjected  to  operations  on  this  account.  For  these 
reasons  it  becomes  apparent  that  any  and  every  treat- 
ment of  intrinsic  exophoria,  whatever  may  be  the  cause, 
must  be  directed  toward  the  externi  or  toward  the  in- 
terni.  An  exophoria  that  is  wholly  muscular,  all  inner- 
vation  centers  being  normal,  will  show  the  same  num- 
ber of  degrees  in  the  near  as  in  the  far. 

Intrinsic  exophoria  is  of  two  kinds,  sthenic  and  asthen- 
ic.  The  quantity  of  the  error  does  not  determine  its  char- 
acter. Only  the  abduction  and  the  abversion  tests,  in  any 
given  case,  can  tell  the  operator  that  the  error  is  sthenic 
or  that  it  is  asthenic.  Exophoria  with  abduction  of  less 
than  8°  and  abversion  of  less  than  50°  is  asthenic,  and 
clearly  indicates  that  the  externi  should  not  have  their 
tension  lessened,  and  just  as  clearly  indicates  that  the 
interni  must  have  their  tension  increased.  Exophoria 
with  abduction  of  more  than  8°  and  abversion  of  more 
than  50°  is  sthenic,  and  the  case  should  be  treated  with 
the  view  of  lessening  the  tension  of  the  externi. 

Tests  in  myopic  and  emmetropic  cases  will  always 
show  the  full  amount  of  intrinsic  exophoria  in  the  far. 
In  the  near  test  of  a  myope,  the  intrinsic  exophoria  will 
have  the  associated  pseudo-exophoria  added  to  it.  If  the 
emmetrope  does  not  show  the  same  exophoria  in  the  near 


318  EXOPHORIA. 

as  in  the  far,  it  is  increased  or  diminished  because  of 
an  abnormal  development  of  the  ciliary  muscles.  If  the 
ciliary  muscles  are  hyper-developed,  there  will  be  more 
exophoria  in  the  near  than  in  the  far,  for  the  reason  that 
an  impulse  less  powerful  than  normal  is  required  of  the 
brain-center  controlling1  them,  so  that  a  correspondingly 
slight  associated  impulse  is  sent  to  the  interni.  'If  the 
ciliary  muscles  are  subnormally  developed,  they  will  re- 
quire an  impulse  more  powerful  than  the  normal,  and  a 
correspondingly  strong  associated  impulse  must  be  sent 
to  the  interni,  causing  a  pseudo-esophoria,  which,  to  a 
certain  extent,  would  neutralize  the  intrinsic  exophoria. 

The  hyperope  will  always  show  less  than  the  full 
amount  of  intrinsic  exophoria  in  both  the  far  and  the  near 
tests,  for  the  reason  that  hyperopia  always  has  a  pseudo- 
esophoria  associated  with  it,  which  neutralizes  in  part  an 
existing  intrinsic  exophoria. 

PSEUDO-EXOPHORIA. — There  can  be  but  two  causes 
for  this  condition.  One  is  myopia,  or  myopic  astigma- 
tism; the  other  is  hyper-development  of  the  ciliary  mus- 
cles, making  it  necessary  for  the  centers  controlling  them 
to  generate  a  less  powerful  nerve  current  than  would  be 
required  by  these  muscles  if  normally  developed. 

When  the  cause  is  myopia,  or  myopic  astigmatism,  the 
pseudo-exophoria  shows  itself  only  in  the  near,  and  is 
due  to  the  fact  that  the  guiding  sensation  calls  either  for 


EXOPHORIA.  319 

no  nerve  force  to  excite  ciliary  action  or  for  a  quantity 
less  than  is  required  by  an  emmetrope,  depending-  on 
the  amount  of  the  focal  error;  and  a  correspondingly 
slight  associated  impulse  is  sent  to  the  interni.  If  the 
point  of  view  is  16  inches  distant,  there  should  be  1.8°  of 
pseudo-exophoria  for  each  dioptre  of  myopia  up  to  2.50 
D,  and  .9°  for  each  dioptre  of  myopic  astigmatism  up  to 
5  D.  This  kind  of  pseudo-exophoria  does  one  of  three 
things:  (a)  it  increases  an  intrinsic  exophoria  in  the  near, 
(b)  it  shows  an  exophoria  in  the  near  when  there  is  real 
orthophoria,  or  (c)  it  lessens  an  intrinsic  esophoria  in  the 
near. 

When  the  pseudo-exophoria  is  due  to  a  hyper-develop- 
ment of  the  ciliary  muscles  and  the  patient  is  an  emme- 
trope, the  error  will  show  itself  only  in  the  near  test. 
If  a  1.50  D  impulse  is  all  that  is  necessary  to  effect  a  3 
D  contraction  of  the  ciliary  muscles,  the  pseudo-exopho- 
ria, with  the  test  object  at  13  inches,  should  be  2.7°. 
This  may  manifest  itself  in  the  same  three  ways  as  that 
caused  by  myopia.  Strictly  speaking,  a  pseudo-exopho- 
ria cannot  exist  in  a  hyperope;  although,  as  shown  in  the 
chapter  on  esophoria,  the  hyperope  who  has  hyper-devel- 
oped ciliary  muscles  will  show  a  less  amount  of  pseudo- 
esophoria  than  would  be  shown  if  these  muscles  were  of 
normal  development.  The  difference  in  amount  is  equiv- 
alent to  pseudo-exophoria. 


320  EXOPHORIA. 

When  the  far  test  shows  orthophoria  and  the  near  test 
shows  exophoria,  the  error  is  pseudo  in  character,  and  is 
dependent  on  one  or  other  of  the  two  causes  above  men- 
tioned; and  the  same  is  true  when  an  exophoria  is  less  in 
the  far  than  it  is  in  the  near.  The  same  explanation 
applies  when  there  is  esophoria  in  the  far  and  exophoria 
in  the  near.  If  in  an  emmetrope  there  is  more  exophoria 
in  the  far  than  there  is  in  the  near,  the  ciliary  muscles 
are  subnormally  developed,  and  require  an  excessive  im- 
pulse to  make  them  perform  their  work.  The  associated 
impulse  to  the  interni  is  correspondingly  great. 

There  is  a  form  of  exophoria  not  yet  referred  to  in  this 
chapter,  and  probably  not  fully  set  forth  in  any  book. 
The  cause  unquestionably  resides  in  the  third  conju- 
gate innervation  center,  and  is  structural  in  character; 
in  other  words,  the  third  conjugate  innervation  center  is 
subnormally  developed,  and,  for  this  reason,  sends  a  feeble 
impulse  to  the  interni.  The  most  exaggerated  manifes- 
tation of  this  condition  would  lead  one  to  judge  that  this 
brain-center  is  entirely  absent,  for  occasionally  a  case  is 
seen  who  has  no  power  of  convergence.  Such  a  person 
enjoys  binocular  vision  in  the  distance,  but  has  only  mo- 
nocular vision  in  the  near.  In  such  a  case  there  is  no  ad- 
duction power,  for  the  one  visual  axis  cannot  be  made  to 
approach  the  other.  Abduction  will  be  normal  or  even 
above  the  normal.  Adversion  is  unimpaired,  showing 


EXOPHORIA.  321 

that  the  fourth  and  fifth  conjugate  innervations  have  full 
sway.  The  abversion  of  the  right  eye  equals  the  adver- 
sion  of  the  left  eye,  and,  vice  versa,  the  abversion  of  the 
left  eye  equals  the  adversion  of  the  right  eye.  In  these 
movements  the  visual  axes  are  kept  parallel,  as  when 
the  eyes  are  looking  straight  ahead.  That  the  condition 
is  congenital  in  most  cases  is  shown  by  the  fact  that 
there  is  no  diplopia  in  the  near.  This  must  be  due  to  an 
acquired  mental  suppression  of  images  that  fall  on  the 
temporal  half  of  the  retina,  or,  at  least,  a  portion  of  it. 
The  power  of  mental  suppression  can  be  acquired  only 
in  the  earliest  years  of  life.  Hansell  &  Reber  speak 
of  a  patient  in  whom  this  loss  of  convergence  power 
was  acquired,  the  result  of  some  disease  process  in 
the  part  of  the  brain  in  which  is  located  the  con- 
vergence center.  It  is  reasonable  to  suppose  that  this 
center  might  be  destroyed  by  disease.  In  such  a  case, 
however,  diplopia  would  exist  everywhere  except  in  the 
distance. 

If  the  third  innervation  center  can  be  entirely  absent 
in  one  person  and  be  present  and  fully  developed  in 
another,  it  is  reasonable  to  conclude  that  in  still 
another  it  may  be  present,  but  in  a  state  of  subnormal 
development.  There  may  be  as  many  different  grades 
of  development  of  this  as  there  are  individuals;  but  in 
the  majority  of  persons  this  center  is  able,  doubtless, 


322  EXOPHORIA. 

to  generate  1°  of  impulse  for  every  1°  of  convergence, 
in  association  with  the  center  of  the  ciliary  muscles. 

Subnormal  development  of  this  center  must  manifest 
itself  in  an  exophoria  in  the  near  many  degrees  in  excess 
of  the  exophoria  in  the  far  (of  itself  it  can  never  cause 
exophoria  in  the  far,  but  it  may  be  associated  with  some 
of  those  conditions  that  cause  intrinsic  exophoria);  or,  if 
there  is  orthophoria  or  even  slight  esophoria  in  the  far, 
there  will  be  considerable  exophoria  in  the  near.  The 
two  ordinary  causes  of  pseudo-exophoria — that  is,  myo- 
pia and  hyper-developed  ciliary  muscles — will  not  cause 
more  than  5°  of  the  error.  A  greater  degree  of  varia- 
tion between  the  far  and  the  near  tests  than  this,  in  the 
exophoric  direction,  must  be  attributed  to  a  subnormally 
developed  third  conjugate  brain-center.  A  diagnostic 
feature  of  this  condition  is  the  manifestation  of  very  low 
abduction  power — much  lower  than  is  found  in  intrinsic 
exophoria  of  the  same  degree. 

It  is  barely  possible  that  a  failure  of  connection  be- 
tween the  ciliary  center  and  the  convergence  center 
accounts  for  the  absence  of  convergence  power  in  some 
cases;  and  a  slight  connection  may  account  for  a  feeble 

convergence. 

TESTS. 

The  cover  test,  allowing  the  eye  to  turn  toward  the 
temple,  will  be  attended  by  a  resetting  of  the  eye  to- 


EXOPHORIA.  323 

ward  the  nose  when  the  cover  is  removed,  and  the  false 
object  will  move  rapidly  toward  the  corresponding-  side 
until  fused  with  the  true  object.  The  examiner  can 
often  see  the  resetting  of  the  eye,  but  not  so  readily  as 
an  intelligent  patient  can  detect  the  apparent  movement 
of  the  test  object. 

The  red  glass,  in  the  higher  grades  of  exophoria,  will 
develop  crossed  diplopia.  The  distance  between  the  red 
light  and  the  true  light  will  give  a  fair  idea  of  the  quan- 
tity of  the  error.  This  test,  resulting  in  crossed  diplo- 
pia, practically  always  indicates  operative  treatment; 
but  since  it  does  not  show  whether  the  case  is  sthenic  or 
asthenic,  it  cannot  indicate  the  character  of  the  opera- 
tion to  be  done. 

The  double  prism  held  before  the  right  eye  so  that  the 
two  lights  seen  through  it  shall  be  in  the  same  vertical 
line,  the  light  seen  by  the  left  eye  will  be  to  the  right, 
if  there  is  exophoria.  The  extent  of  the  error  is  shown 
by  that  prism,  base  toward  the  nose,  that  will  place  the 
middle  light  in  line  with  the  other  two.  This  test,  so 
far  as  it  goes,  is  safe  and  accurate;  but  it  cannot  show 
whether  the  exophoria  is  sthenic  or  asthenic,  and  cannot, 
therefore,  be  relied  upon  in  answering  the  question: 
"What  operation,  if  any,  shall  be  done?" 

The  single  six-degree  prism,  held  base  up  before  the 
right  eye,  with  the  axis  perfectly  vertical,  is  as  reliable 


324  EXOPHORIA. 

as  the  double  prism,  though  one  can  never  be  so  certain 
that  the  axis  is  vertical  as  he  can  be  when  using-  the  dou- 
ble prism.  The  lower,  or  false,  light  will  be  on  the  op- 
posite side — crossed  diplopia.  The  prism,  base  in,  that 
brings  it  directly  under  the  true  candle,  measures  the 
amount  of  the  exophoria.  Like  the  double-prism  test, 
this  one  does  not  show  whether  the  exophoria  is  sthenic 
or  asthenic. 

The  rod  test  is  less  reliable  in  exophoria  than  in  eso- 
phoria,  for  the  reason  that  images  displaced  in  the  tem- 
poral part  of  the  retinal  fusion  area  seem  to  excite  a 
greater  demand  for  fusion  than  when  displaced  in  the 
nasal  part.  Nevertheless,  if  the  exophoria  is  sufficiently 
great,  the  rod  held  with  its  axis  horizontal  before  the 
right  eye  will  cause  the  streak  of  light  to  appear  to  the 
left  of  the  candle.  The  prism,  base  in,  that  brings  this 
vertical  streak  into  the  candle,  measures,  but  not  with 
accuracy,  the  exophoria.  It  always  shows  less  exopho- 
ria than  really  exists.  Maddox  thinks  that  a  red  rod 
makes  this  test  practically  perfect,  if,  at  the  same  time, 
a  plain  green  or  blue  glass  be  held  before  the  other  eye. 

The  safe,  sure,  speedy,  and  easy  test  for  exophoria  is 
by  means  of  the  phorometer,  and  of  all  the  phorometers 
the  monocular  is  the  most  reliable  in  its  results.  The 
method  of  testing  for  exophoria  is  the  same  as  that  for 
esophoria,  the  position  of  the  false  object  always  deter- 


EXOPHORIA.  325 

mining'  whether  it  is  the  one  or  the  other  error.  It  is 
always  on  the  opposite  side  in  exophoria.  The  error  is 
measured  by  revolving-  the  rotary  prism  until  the  false 
object  is  brought  under  the  true  object,  when  the  index 
will  mark  the  quantity  of  the  error.  In  the  same  way 
the  other  eye  should  be  tested.  In  the  phorometer  test, 
as  in  all  others,  the  exophoria  at  16  inches  should  also 
be  determined. 

The  next  step  is  the  taking-  of  the  abduction.  This  is 
the  chief  means  for  determining  whether  the  exophoria 
is  sthenic  or  asthenic.  Unless  the  character  of  the  error 
is  known,  it  is  not  possible  to  resort  to  rational  treat- 
ment. Whatever  means  may  have  been  used  in  detect- 
ing- the  imbalance,  the  lifting-  power  of  the  externi — ab- 
duction— must  be  taken. 

This  can  be  done,  but  not  quickly  nor  accurately,  by 
holding-  prism  after  prism,  base  in,  before  one  eye,  until 
the  patient  can  no  longer  fuse  the  imag-es.  The  chief 
objection  to  this  method  is  the  uncertainty  about  the 
axis  of  this  prism  being-  perfectly  horizontal.  The 
rotary  prism  of  the  phorometer,  the  instrument  being- 
perfectly  leveled,  is  the  quickest  and  best  means  for  de- 
termining- abduction  or  any  other  kind  of  duction.  To 
test  abduction  with  the  rotary  prism,  the  handle  must 
be  horizontal  and  the  index  must  start  from  zero.  Mov- 
ing the  index  toward  the  temple  it  must  be  stopped  the 


326  EXOPHORIA. 

moment  the  patient  says  the  test  object  becomes  double. 
The  index  stands  opposite  the  number  indicating  the  de- 
gree of  abduction.  If  this  is  less  than  8°,  the  exophoria 
is  asthenic;  if  more  than  8°,  it  is  sthenic.  If  abduction 
is  just  8°,  since  it  would  indicate  that  the  tension  of  the 
externus  should  not  be  lessened,  the  exophoria  should  be 
classed  as  asthenic,  from  an  operative  standpoint. 

Lastly,  abversion  should  be  taken  either  with  the 
perimeter  or  the  tropometer.  This  will  usually  be  found 
less  than  50°  if  abduction  is  low,  and  more  than  50°  if 
abduction  is  high. 

While  abduction  and  abversion  are  to  be  relied  on 
most,  adduction  and  adversion  should  always  be  taken. 
In  fact,  the  study  of  no  one  muscle  error  is  complete 
until  all  other  errors  have  either  been  found  or  elimi- 
nated; and  the  individual  strength  of  every  muscle  must 
be  known.  It  is  only  in  this  way  that  the  real  nature 
of  an  exophoria  can  be  known,  and  without  this  knowl- 
edge, rational  treatment  is  impossible. 

COMPLICATIONS  OF  EXOPHORIA.  —  These  are  the 
same  as  found  in  connection  with  the  study  of  esophoria. 
They  need  only  be  mentioned  here,  as,  under  the  head 
"Treatment,'-'  it  wrill  be  shown  how  they  modify  the 
management  of  the  exophoria.  They  are:  myopia  and 
myopic  astigmatism,  hyperopia  and  hyperopic  astigma- 
tism, and  plus  and  minus  cyclophoria.  Thus  it  appears 


EXOPHORIA.  327 

that  not  only  the  relationship  of  every  pair  of  muscles, 
and  the  condition  of  every  individual  muscle,  must  be 
known,  but  the  refraction  must  also  be  understood,  if 
one  would  deal  successfully  with  exophoria. 

SYMPTOMS. 

The  subjective  symptoms — or,  more  correctly  speak- 
ing-, the  reflex  nervous  symptoms — caused  by  exophoria 
are  those  outlined  in  Chapter  III.  of  this  book,  under 
the  head  "Symptoms  of  Heterophoria. "  The  symp- 
toms, whatever  they  may  be,  are  not  due  to  the  inher- 
ent tension  of  the  externi  and  their  synergists,  but  to 
the  nervous  tension  of  the  interni  and  their  synergists, 
necessary  for  maintaining  binocular  singular  vision. 
A  symptom  of  which  exophorics  very  commonly  com- 
plain is  a  blurring  or  running  together  of  the  letters  of 
the  printed  page,  after  more  or  less  prolonged  reading. 
At  such  times  the  reader  feels  compelled  to  close  the 
eyes  tightly  before  resuming  his  reading.  Another 
symptom,  often  present  when  near  work  is  being  done, 
is  a  heavy,  sleepy  feeling  of  the  upper  lids,  also  a  stiff 
feeling  of  the  upper  lids,  as  if  they  were  adherent  to  the 
globes.  Prolonged  near  work  congests  the  margins  of 
the  lids,  even  developing  a  marginal  blepharitis,  more 
commonly  in  exophoria  than  in  any  other  form  of  hetero- 
phoria.  A  drawing  sensation  on  the  nasal  side  of  the 


328  EXOPHORIA. 

eyes  is  often  complained  of.  There  is  no  facial  expres- 
sion or  pose  of  the  head  that  is  peculiar  either  to  exopho- 
ria  or  to  esophoria. 

TREATMENT. 

NON- OPERATIVE. — In  pseudo-exophoria  the  cause 
should  always  be  removed,  if  practicable,  by  non-opera- 
tive means.  The  pseudo-exophoria  caused  by  myopia 
and  found  only  in  the  near,  when  it  serves  to  neutralize 
a  part  of  an  inherent  esophoria,  should  be  allowed  to 
continue  until  the  esophoria  has  been  cured  by  prisms 
in  positions  of  rest,  by  exercise  of  the  externi,  or  by  op- 
erations. By  the  non-treatment  of  a  pseudo-exophoria 
of  this  character  is  meant  that  the  myopic  correction 
should  not  be  worn  in  near  work.  For  distant  seeing 
the  myopic  correction  should  always  be  worn,  for  it 
neither  adds  to  nor  diminishes  any  form  of  heterophoria. 
If  a  myope  is  orthophoric  for  distance,  the  concave  lenses 
should  be  worn  for  all  purposes.  With  the  lenses  on  for 
distant  seeing"  there  will  still  be  orthophoria;  with  them 
on  in  near  work  the  pseudo-exophoria  is  relieved  and  the 
patient  becomes  orthophoric  in  the  near  as  well.  If  the 
myope  is  exophoric  in  the  distance,  the  concave  lenses 
should  be  worn  for  all  purposes.  The  distant  test  will 
show  the  same  exophoria  with  and  without  the  lenses. 
In  the  near  test  without  the  lenses,  the  exophoria  shown 
will  be  the  intrinsic  plus  the  pseudo;  and  with  the 


EXOPHORIA.  329 

lenses  will  be  only  the  intrinsic,  the  pseudo-exophoria 
having  been  cured  by  the  establishment  of  the  normal 
relationship  between  the  center  of  convergence  and  the 
center  of  ciliary  action. 

The  pseudo-exophoria  caused  by  over-development  of 
the  ciliary  muscles,  requiring  less  than  a  1  D  impulse  to 
effect  a  1  D  contraction  of  these  muscles,  is  best  treated 
by  the  wearing  of  concave  lenses,  only  in  the  near  if  the 
patient  is  an  emmetrope,  but  both  in  the  far  and  in  the 
near  if  the  patient  is  slightly  hyperopic.  By  so  doing  a 
pseudo-esophoria  is  developed  which  lessens  the  exopho- 
ria.  If  the  diagnosis  is  correct — that  is,  if  the  exopho- 
ria  is  wholly  or  in  part  pseudo — the  wearing  of  concave 
lenses  will  be  attended  by  a  source  of  relief.  "When 
they  cause  discomfort,  they  should  be  discarded;  for  the 
exophoria  is  due  to  some  other  cause  than  hyper-devel- 
opment of  the  ciliary  muscles. 

It  will  be  remembered  by  many  that  J.  J.  Chisolm,  of 
Baltimore,  was  in  the  habit,  for  many  years,  of  pre- 
scribing concave  cylinders  when  his  patients  had  hy- 
peropic astigmatism.  Although  he  did  not  so  teach, 
nevertheless  his  patients  that  were  benefited  had  exo- 
phoria. An  esophoric  patient  would  not  have  tolerated 
such  lenses. 

Patients  who  are  hyperopic  and  have  either  pseudo 
or  inherent  exophoria  should  never  be  given  the  full 


330  EXOPHORIA. 

correction  of  the  hyperopia,  for  the  imbalance  would 
be  made  worse.  If  the  hyperopia  is  less  than  2  diop- 
tres and  the  exophoria  in  the  near  is  more  than  4°,  no 
correction  should  be  given;  if  more  than  2  dioptres,  only 
the  excess  should  be  corrected.  After  an  exophoria  has 
been  cured  by  exercise  or  by  operation,  a  full  correction 
of  the  hyperopia  may  be  given,  but  in  most  cases  0.50  D 
should  go  uncorrected. 

What  has  been  said  of  myopic  and  hyperopic  correc- 
tions, in  cases  of  exophoria,  applies  proportionately  to 
astigmatic  (myopic  or  hyperopic)  corrections.  How  to 
deal  with  these  errors  when  there  is  a  complicating  eso- 
phoria  has  been  emphasized  in  Chapter  IV. 

Those  unfortunate  subjects  who  have  no  converging 
power,  probably  because  of  absence  of  the  third  con- 
jugate innervation  center,  cannot  be  relieved  by  either 
lenses,  prisms,  exercise,  or  operations. 

INHERENT  EXOPHORIA. — The  treatment  of  the  two 
forms  of  inherent  exophoria  is  the  same,  so  far  as  con- 
cerns non-operative  means.  The  first  of  these  is  prisms 
in  positions  of  rest  (bases  in)  for  the  weak  interni.  The 
full  correction  of  exophoria  by  prisms  should  not  be  at- 
tempted; probably  only  a  half  correction  of  the  error 
should  be  given.  Maddox  suggests  a  correction  of  half 
or  a  third  of  the  distant  and  a  quarter  of  the  near  exo- 
phoria. When  there  is  no  complicating  cyclophoria,  the 


EXOPHORIA.  331 

prismatic  effect  should  be  equally  divided  between  the 
two  eyes,  and  the  axes  of  the  prisms  should  be  perfectly 
horizontal.  The  same  rule  holds  good  when  there  is  a 
hyperphoria  of  one  eye  and  a  cataphoria  of  the  other.  If 
there  is  a  complicating-  plus  cyclophoria  without  any 
hyperphoria,  the  prismatic  effect  should  be  equally  di- 
vided between  the  two  eyes;  but  the  axis  of  each  should 
be  tilted  down  at  the  temporal  end,  so  as  to  make  the 
extern!  tort  the  eyes  in  while  turning-  them  out  to  fuse 
the  displaced  images.  The  axes  should  be  tilted  in  the 
opposite  direction  if  the  complication  is  a  minus  cyclo- 
phoria. When  the  complication  is  a  plus  cyclophoria 
with  a  right  hyperphoria  and  a  left  cataphoria,  the  exo- 
phoric  prism  should  be  placed  only  before  the  hyper- 
phoric  eye  and  its  axis  should  be  tilted  down  at  the 
temporal  end.  The  muscular  action  necessary  for  over- 
coming the  prism  will  turn  the  eye  out  and  down  and 
tort  it  in.  If  discomfort  results,  it  will  be  due  to  the  work 
that  the  inferior  rectus  has  had  to  do  to  overcome  the 
prismatic  displacement.  If  any  prism  is  placed  before 
the  left  (cataphoric)  eye,  its  axis  should  be  perfectly  hori- 
zontal, for,  if  tilted  down  at  the  temporal  end,  it  would 
favor  the  cyclophoria,  but  increase  the  cataphoria;  while, 
if  tilted  up,  it  would  force  a  correction  of  the  cataphoria, 
but  would  increase  the  plus  cyclophoria.  If  there  is  doubt 
as  to  whether  the  axes  of  the  exophoric  prisms  should 


332  EXOPHORIA. 

be  tilted,  it  is  better  to  place  them  exactly  horizontal. 
Weak  exophoric  prisms,  with  their  axes  perfectly  hori- 
zontal, should  bring  some  relief  to  most  patients.  When 
they  do  not  relieve,  it  thus  becomes  evident  that  one 
externus,  if  not  both,  is  attached  too  high,  and  there  is 
developed  a  plus  cyclophoria. 

The  objection  raised  against  esophoric  rest  prisms, 
that  they  interfere  with  the  law  of  direction,  applies 
with  equal  force  to  prisms  in  positions  of  rest  for  exo- 
phoria. 

Decentration  of  lenses,  in  for  convex  and  out  for  con- 
cave, will  accomplish  the  same  results  for  exophoria  as 
will  prisms  with  bases  in.  The  rules  for  decentration 
are  given  in  Chapter  IV. 

EXERCISE  TREATMENT. 

There  are  two  useful  methods  of  exercising  the  weak 
interni  in  cases  of  exophoria.  The  simplest,  if  not  the 
best,  and  certainly  the  cheapest,  is  the  candle  exercise. 
The  candle  is  mentioned  for  the  reason  that  the  images 
of  its  blaze  stimulate  the  two  retinas  so  as  to  make  it 
more  certain  that  the  center  of  convergence  will  be  ex- 
cited sufficiently  to  converge  the  visual  axes,  as  the  candle 
is  brought  from  arm's  length  to  a  point  six  or  seven  inches 
from  the  eyes.  Images  less  bright,  such  as  those  of  a  pen- 
cil, in  some  cases  would  not  sufficiently  stimulate.  The 


EXOPHORIA.  333 

method  of  conducting-  the  candle  exercise  is  sufficiently 
set  forth  in  Chapter  III.,  to  which  the  reader  is  referred. 
If  properly  conducted  and  continued  sufficiently  long,  it 
will  do  good  in  all  cases  except  those  in  whom  the  interni 
have  attachments  too  high  on  the  globes.  Interni  thus 
attached,  when  exercised  either  with  the  candle  or  by 
means  of  prisms,  will  call  into  simultaneous  action  the 
inferior  obliques,  that  they  may  prevent  the  convergence 
of  the  vertical  axes  of  the  eyes.  In  the  greater  number 
of  cases  this  would  either  add  to  or  develop  a  plus  cyclo- 
phoria  while  curing  the  exophoria.  The  patient  would 
not  be  benefited.  But  when  the  interni  have  the  ideal 
attachments,  or  even  when  they  are  attached  too  low, 
the  candle  exercise,  as  well  as  prism  exercise,  will  do 
good.  In  cases  of  ideal  attachment  only  the  interni  are 
exercised;  in  cases  with  attachment  too  low  every  con- 
traction of  the  interni  is  attended  by  a  contraction  of  the 
superior  obliques,  so  that  development  of  the  interni  is 
attended  by  a  corresponding  development  of  the  superior 
obliques — a  thing  to  be  desired  in  many  cases. 

The  rapidity  of  a  cure  of  exophoria  by  the  candle  ex- 
ercise depends  in  part  on  the  quantity  of  the  exophoria 
and  in  part  on  the  character  of  the  blood  supply  of  the 
interni;  abundant  blood  supply  means  quicker  results. 
Gentle  rhythmic  exercise  will  increase  the  size  and 
power  of  a  muscle,  whether  voluntary  or  involuntary. 


334  EXOPHORIA. 

Permanent  results  follow  such  a  method.  No  one  can 
doubt  that  a  muscle  can  be  developed;  there  is  reasonable 
doubt  if  a  nerve  center  can  be  developed  as  a  result  of 
either  mild  or  severe  stimulation.  A  nerve  cell  is  very 
different  from  a  muscle  fiber. 

PRISM  EXERCISE. 

There  are  two  methods  of  exercising-  the  interni  by 
means  of  prisms.  The  one  is  gentle  rhythmic  ex- 
ercise by  means  of  weak  prisms  witk  their  bases  out; 
the  other  method  is  that  first  suggested  by  Deady, 
and  later  advocated  by  Gould — loading  the  converg- 
ence by  means  of  the  strongest  prisms  possible.  The 
former  is  intended  for  the  strengthening  of  the  mus- 
cles themselves,  while  the  latter  is  designed  to  stim- 
ulate the  convergence  center  to  greater  activity.  The 
advocates  of  the  latter  method  claim  that  exophoria,  in 
most  cases,  is  purely  innervational  and  should  be  cured 
by  forced  stimulation  of  the  convergence  brain-center, 
the  third  conjugate  innervation  center.  That  this  cen- 
ter is  susceptible  to  excessive  stimulation  cannot  be  de- 
nied, but  it  is  doubtful  if  this  should  be  done.  It  is  cer- 
tainly more  rational  to  develop  the  interni  so  as  to  make 
them  respond  normally  to  the  impulse  that  the  brain - 
center  can  easily  generate  in  its  real,  though  it  may  be 
subnormal,  state  of  development.  If  it  were  possible  to 


EXOPHORIA.  335 

enlarge  the  capacity  of  a  brain-center,  as  it  is  possible  to 
increase  the  size  and  power  of  a  muscle,  the  Deady  method 
would  not  be  objectionable.  The  reader  is  ag-ain  referred 
to  Chapter  III.,  where  the  method  is  described. 

In  the  rhythmic  exercise  of  the  interni  by  prisms, 
the  design  is  to  produce  slight  contractions  by  means  of 
weak  prisms  (from  1°  to  8°)  with  their  bases  out,  to  be 
followed  by  complete  relaxation,  each  contraction  and 
relaxation  to  last  about  three  seconds,  throughout  a  sitting 
of  not  more  than  ten  minutes.  The  exercise  should  al- 
ways stop  short  of  fatigue,  for  exercise  that  tires  does 
not  build.  To  get  practically  complete  relaxation,  the 
object  of  fixation  should  be  twenty  feet  distant.  Per- 
sistent exercise,  after  this  method,  in  low  degrees  of  in- 
herent exophoria,  will  produce  permanent  results.  This 
method  is  fully  set  forth  in  Chapter  III. 

In  high  degrees  of  intrinsic  exophoria,  non-operative 
measures  will  be  productive  of  but  little,  and  that  little 
will  be  slow  of  accomplishment.  Exophoria  in  the 
distance  of  4°  or  more,  and  an  exophoria  in  the  near 
equal  to  the  angle  of  convergence  at  that  point,  give 
little  promise  of  yielding  to  non-operative  means.  An 
exophoria  that  gives  diplopia  in  the  distance  under 
the  red  glass  test,  is  practically  always  a  case  for 
surgical  treatment.  All  cases  not  showing  good  re- 
sults, in  a  reasonable  length  of  time,  under  non-oper- 


336  EXOPHORIA. 

ative  measures,  should  be  given  the  advantage  offered 
by  skilled  surgery. 

The  object  in  view  when  exercising  the  interni  in  ex- 
ophoria  is  to  so  develop  them  that  they  may  respond 
normally  to  a  normal  nerve  impulse — 1°  of  contraction 
for  every  degree  of  impulse. 

OPERATIVE  TREATMENT. 

Before  any  operation  for  exophoria  is  done,  the  pos- 
sibility of  a  cure  by  non-operative  means  should  be  elim- 
inated, and  the  condition  of  every  extrinsic  ocular  muscle 
should  be  known.  Complicating  muscle  imbalances  must 
be  taken  into  account,  and,  if  possible,  should  be  cor- 
rected by  the  operations  for  the  exophoria.  In  uncom- 
plicated cases  of  exophoria,  and  in  cases  complicated 
only  by  hyperphoria  of  one  eye  and  cataphoria  of  the 
other,  the  operations  must  either  diminish  the  tension  of 
the  extern!  or  increase  the  tension  of  the  interni.  When 
the  exophoria  is  complicated  by  a  cyclophoria,  not  only 
must  the  muscle  tension  be  altered,  but  the  muscle  plane 
must  also  be  changed. 

In  sthenic  exophoria  the  externi  should  be  first  sub- 
jected to  the  operation  of  partial  tenotomy,  with  the 
view  of  reducing  their  tension.  The  case  being  uncom- 
plicated, the  tenotomy  should  be  central.  The  operative 
effect  should  be  equally  divided  between  the  two  externi, 


EXOPHORIA.  337 

and  should  not  be  so  extensive  as  to  reduce  abduction  be- 
low 8°  or  abversion  below  50°.  In  no  case  of  exophoria 
should  a  complete  tenotomy  of  an  externus  ever  be  done, 
for  the  reason  that  the  risk  of  reducing  both  the  duction 
and  version  power  below  the  normal  would  be  too  great. 
After  the  two  partial  tenotomies,  any  remaining  exo- 
phoria that  cannot  be  cured  by  non- operative  meas- 
ures should  be  still  further  relieved  by  a  straight- 
forward shortening  of  one  or  both  interni,  with  the 
view  of  increasing  tension  without  changing  the  plane 
of  rotation. 

When  there  is  a  complication  of  hyperphoria  and  cata- 
phoria  only,  the  operations,  whether  partial  tenotomies  or 
shortenings,  should  be  done  as  if  no  complication  existed. 
At  some  other  time  the  vertical  error  must  be  given  the 
proper  treatment. 

A  sthenic  exophoria  that  is  complicated  by  a  plus  cy- 
clophoria  only  should  be  treated  with  the  view  of  lessen- 
ing the  tension  of  both  externi  and  lowering  their  planes 
of  action.  This  would  be  accomplished  by  cutting  the 
upper  and  central  fibers  of  each  externus  as  nearly  alike 
as  possible,  leaving  the  lower  fibers  intact.  The  three- 
fold effect  of  these  two  operations  would  be:  (a)  lessen- 
ing or  curing  the  exophoria;  (b)  correction,  wholly  or  in 
part,  of  the  plus  cyclophoria;  (c)  the  production  of  a  dou- 
ble cataphoria. 


338  EXOPHORIA. 

A  sthenic  exophoria  complicated  by  a  plus  cyclopho- 
ria  and  a  right  hyperphoria  and  left  cataphoria  should 
be  subjected  first  to  a  partial  marginal  tenotomy  of  the 
externus  of  the  hyperphoric  eye.  The  operation  of  cut- 
ting the  upper  and  central  fibers  of  this  externus  would  be 
attended  by  these  three  results:  (a)  lessening  of  the  ex- 
ophoria;  (b)  a  partial  or  complete  correction  of  the  plus 
cyclophoria;  (c)  the  production  of  a  cataphoria  equal  to, 
or  a  little  less  than,  the  cataphoria  in  the  other  eye.  If 
any  remaining1  exophoria  should  still  be  complicated  with 
plus  cyclophoria  and  left  cataphoria,  the  second  opera- 
tion should  be  a  shortening  of  the  left  internus  in  such  a 
way  as  to  both  increase  its  tension  and  elevate  its  plane 
of  action.  This  would  have  three  results:  (a)  still  further 
diminishing,  if  not  curing,  the  exophoria;  (b)  a  further 
correction  of  the  plus  cyclophoria;  (c)  an  elevation  of  the 
cataphoric  eye  so  as  to  bring  it  as  nearly  as  possible 
in  the  same  horizontal  plane  with  the  eye  that  was  pri- 
marily hyperphoric.  Should  the  first  operation  cure  the 
complicating  plus  cyclophoria,  even  if  the  hyperphoria 
were  not  cured,  the  remaining  exophoria  should  be  re- 
lieved by  a  central  partial  tenotomy  of  the  externus  of 
the  left  eye,  which  would  alter  its  tension  without  chang- 
ing its  plane  of  action. 

Asthenic  exophoria  uncomplicated  should  be  treated 
by  straight-forward  shortening  of  both  interni,  the  op- 


EXOPHORIA.  339 

erative  effect  being  as  equally  divided  between  them  as 
possible.  In  this  way  their  tension  would  be  increased, 
but  their  planes  of  rotation  would  not  be  changed.  The 
same  operations  should  be  done  when  the  exophoria  is 
complicated  by  hyperphoria  and  cataphoria.  Operations 
for  a  lateral  error  should  attempt  the  simultaneous  cor- 
rection of  a  vertical  error  only  when  there  is  a  complicat- 
ing cyclophoria. 

Asthenic  exophoria,  complicated  by  a  plus  cyclophoria 
only,  should  have  both  conditions  relieved  by  shortenings 
of  both  interni  in  such  a  way  as  to  increase  their  tension 
and  elevate  their  planes.  The  triple  effect  would  be: 
(a)  correction  of  the  exophoria;  (b)  cure  of  the  plus 
cyclophoria;  (c)  the  production  of  a  double  hyperphoria. 
When  the  complication  is  not  only  a  plus  cyclophoria,  but 
a  right  hyperphoria  and  left  cataphoria  as  well,  the  first 
operation  should  be  a  shortening  of  the  left  internus  in 
such  a  way  as  to  both  increase  its  tension  and  elevate  its 
plane.  These  would  be  the  effects  of  this  operation:  (a) 
correction,  wholly  or  in  part,  of  the  exophoria;  (b)  a  par- 
tial or  complete  cure  of  the  cyclophoria;  (c)  the  produc- 
tion of  a  double  hyperphoria.  If  the  internus  of  the 
right  eye  must  be  operated  upon,  the  shortening  must 
be  straight-forward,  even  if  the  two  complications  still 
existed;  for  an  elevation  of  its  plane  would  increase  the 
hyperphoria  while  lessening  the  plus  cyclophoria,  and 


340  EXOPHORIA. 

lowering1  its  plane  would  increase  the  cyclophoria  while 
diminishing1  the  hyperphoria. 

If  a  minus  cyclophoria,  which  is  rare,  should  alone 
complicate  an  exophoria,  the  marginal  tenotomies  of  the 
externi  would  be  below,  and  the  shortenings  of  the  in- 
terni  would  have  to  be  done  so  as  to  depress  their  plane 
of  rotation.  If  the  minus  cyclophoria  \vith  a  hyperpho- 
ria and  cataphoria  should  complicate  an  exophoria,  a 
lower  marginal  tenotomy  of  an  externus  should  be  per- 
formed only  on  the  externus  of  the  cataphoric  eye;  while 
a  shortening  of  an  internus  with  depression  of  its  plane 
should  be  done  only  on  the  internus  of  the  hyperphoric 
eye,  for  reasons  that  are  apparent. 

The  chief  object  in  operating  for  exophoria,  whether 
the  operation  be  partial  tenotomies  of  the  externi  for 
sthenic  exophoria  or  shortenings  of  the  interni  for  as- 
thenic  exophoria,  is  to  so  change  the  relative  tension  of 
the  interni  as  to  enable  them  to  respond  normally  to  a 
normal  impulse  from  the  third  conjugate  innervation 
center — 1°  degree  of  convergence  for  every  degree  of  im- 
pulse— and  thus  establish  harmony  between  the  externi 
and  the  interni. 

The  change  of  the  plane  of  action,  though  of  vast  im- 
portance, depends  solely  on  the  existence  of  a  compli- 
cating cyclophoria. 


CHAPTER  VI. 


HYPERPHORIA  AND  CATAPHORIA. 


THESE  conditions  can  be  studied  intelligently  only  when 
the  head  is  in  the  primary  position,  with  the  test  object 
on  the  line  of  intersection  of  the  extended  median  and 
horizontal  fixed  planes  of  the  head.  The  object  should 
be  twenty  feet  distant  from  the  eyes.  If  there  is  no  imbal- 
ance of  the  vertically-acting"  muscles  and  the  lateral 
recti  are  properly  attached  and  the  eyes  are  contained 
in  orbits  that  have  been  normally  developed,  when  the 
test  object  is  fixed,  the  two  visual  axes  will  lie  in  the  ex- 
tended horizontal  plane,  with  no  tendency  for  either  axis 
to  rise  above  or  dip  below  this  plane.  This  will  be 
shown  under  any  one  or  all  of  the  tests  for  determining 
the  balance  of  the  ocular  muscles.  Such  a  condition,  as 
already  noted  in  Chapter  II.,  is  vertical  orthophoria. 
Hyperphoria  is  a  tendency  of  one  visual  axis  to  rise  above 
this  plane,  the  actual  turning-  easily  occurring-  as  soon 
as  the  eye  is  freed  from  the  control  of  the  guiding-  sen- 
sation, by  any  one  of  the  tests  to  be  given  farther  on. 
Cataphoria  is  a  tendency  on  the  part  of  one  visual  axis 
to  fall  below  this  plane,  the  tendency  becoming  a  turning 

(311) 


342  HYPERPHORIA   AND   CATAPHORIA. 

so  soon  as  the  image  has  been  changed  in  character  or 
position  so  that  no  effort  at  fusion  will  be  made.  Usu- 
ally a  hyperphoria  of  one  eye  is  associated  with  a  cata- 
phoria  of  the  other,  and  the  two  errors  are  practically 
equal.  Occasionally  there  will  be  found  a  case  in  which 
there  is  a  vertical  orthophoria  of  one  eye  and  a  hyperpho- 
ria or  a  cataphoria  of  the  other.  Less  frequently  there 
will  be  double  hyperphoria  or  double  cataphoria. 

Any  one  of  these  errors  makes  it  a  difficult  matter  for 
the  superior  and  inferior  recti  to  obey  the  law  governing 
them — to  wit,  they  must  keep  the  visual  axes  in  the  same 
plane,  in  order  to  help  relate,  properly,  corresponding 
retinal  points. 

CAUSES. — There  are  several  conditions  that  may  cause 
a  vertical  imbalance.  Since  malformation  of  the  orbits 
has  been  emphasized,  in  recent  years,  as  a  cause  of  hy- 
perphoria, this  will  be  studied  first.  Only  in  the  sense 
of  one  orbit's  being  higher  or  lower  than  the  other,  can  a 
malformed  orbit  be  the  only  cause  either  of  a  hyperpho- 
ria or  a  cataphoria.  Fig.  43  represents  the  median  plane 
of  the  head,  A  B;  the  horizontal  plane  of  the  head,  C  D; 
and  the  two  eyes.  The  right  one  is  in  a  normal  orbit,  so 
that  its  vertical  axis  g-h  is  parallel  with  the  median  plane 
of  the  head  and  its  transverse  axis  efis  contained  in  the 
horizontal  plane  of  the  head.  The  left  eye  is  represented 
as  contained  in  a  malformed  orbit,  in  the  sense  that  it  is 


HYPERPHORIA  AND  CATAPHORIA. 


343 


lower  than  the  fellow  orbit;  therefore  the  contained  eye 
is  lower  than  its  fellow,  as  is  shown  by  its  transverse 
axis  flying  below  the  fixed  horizontal  plane  of  the  head, 
C  D.  It  will  be  seen  that  the  vertical  axis  g-h  is  parallel 
with  the  median  plane  A  B.  The  muscles  of  these  two 
eyes  may  be  supposed  to  be  perfectly  balanced.  Under 
the  phorometer  test  of  the  vertically-acting-  muscles,  the 


B 

Fig-  43- 


rig-ht  eye  would  show  orthophoria,  but  the  left  eye  would 
show  cataphoria.  In  binocular  fixation  of  a  point  lying- 
in  the  extended  horizontal  plane  of  the  head,  the  visual 
axis  of  the  rig-lit  eye,  the  muscles  being-  in  a  state  of 
equilibrium,  would  point  to  the  object;  while  the  visual 
axis  of  the  left  eye  would  have  to  be  raised  by  the  supe- 
rior rectus  and  inferior  oblique,  so  as  to  intersect  its  fel- 
low at  the  point  of  view.  Thus  elevated,  its  vertically- 


344 


HYPERPHORIA  AND  CATAPHORIA. 


acting  muscles  cannot  be  in  a  state  of  equilibrium.  Un- 
der test  this  eye  would  drop  into  a  state  of  equilibrium 
for  all  its  muscles  and  would  thus  show  cataphoria.  No 
posing-  of  the  head  would  change  the  condition  or  lessen 
the  error.  The  right  eye  under  test  would  continue  in 
its  state  of  equilibrium,  and  would,  therefore,  show  verti- 
cal orthophoria. 


B 


Fig. 


A  figure  could  have  been  constructed  showing  the 
right  eye  in  a  normal  orbit,  with  its  axes  properly  re- 
lated to  the  median  and  horizontal  planes  of  the  head; 
and  the  left  eye  in  a  malformed  orbit,  in  the  sense  of  its 
being  higher  than  the  fellow  orbit,  with  its  transverse 
axis  ef  above  the  fixed  horizontal  plane  of  the  head,  al- 
though its  vertical  axis  gh  would  be  parallel  with  the 
median  plane.  The  right  eye  would  show  vertical  ortho- 


HYPERPHORIA  AND  CATAPHORIA. 


345 


phoria,  but  the  left  eye  would  show  hyperphoria.  No 
posing-  of  the  head  can  change  the  relationship  that  these 
two  eyes  bear  to  the  two  fixed  planes  of  the  head. 

Fig-.  44  represents  malformation  of  both  orbits  in  the 
sense  that  the  right  one  is  too  high  and  the  left  one  is 
too  low.  The  vertical  axis  of  each  eye  is  parallel  with 
the  median  plane  of  the  head,  but  the  transverse  axis  of 


-J) 


f 


3 

Fig-  45- 


neither  eye  lies  in  the  horizontal  plane  of  the  head;  that  of 
the  rig-lit  eye  is  above,  while  that  of  the  left  eye  is  below 
it,  but  both  are  necessarily  parallel  with  it.  The  mal- 
position of  the  rig-ht  eye  would  g-ive  to  it  hyperphoria, 
while  the  malposition  of  the  left  eye  would  g-ive  to  it 
cataphoria.  A  state  of  equilibrium  of  the  vertically-act- 
ing- muscles  (granted  to  be  normal)  of  the  right  eye  would 
place  its  axis  above,  but  parallel  with,  the  extended  hor- 
izontal plane  of  the  head;  while  the  same  muscular  state 


346 


HYPERPHORIA  AND  CATAPHORIA. 


of  the  left  eye  would  place  its  visual  axis  below,  but 
parallel  with  this  plane.  No  pose  of  the  head  can  help 
these  eyes  in  the  effort  at  binocular  fixation. 

Fig.  45  represents  a  pair  of  eyes  that  are  set  in  mal- 
formed orbits,  in  the  sense  that  both  are  too  low;  hence 
both  of  these  eyes  have  their  transverse  axes  below  the 
horizontal  plane  of  the  head,  but  parallel  with  it.  This 


B 

Fig.  46. 

kind  of  malformation  gives  a  double  cataphoria,  which 
can  be  detected  with  a  fair  degree  of  readiness  by  means 
of  the  monocular  phorometer,  but  is  more  certainly  and 
more  easily  shown  by  the  proof  test  of  hyperphoria — a 
double  prism,  the  use  of  which,  for  this  purpose,  will  be 
described  under  the  head  "Tests."  A  pose  of  the  head 
cannot  bring1  the  transverse  axes  of  the  eyes  into  the  hor- 
izontal plane  of  the  head,  but  it  can  make  vision  easier. 


HYPERPHORIA  AND  CATAPHORIA.        347 

The  characteristic  pose,  in  such  cases,  is  an  elevation  of 
the  chin.  Such  people  are  high-headed. 

Fig.  46  represents  a  pair  of  eyes  set  in  malformed  or- 
bits, in  the  sense  that  they  are  both  too  hig-h.  The  ver- 
tical axes  are  parallel  with  the  median  plane  of  the  head, 
but  the  transverse  axes  lie  above  the  horizontal  plane, 
though  parallel  with  it.  With  the  head  in  the  primary 
position,  a  point  in  the  extended  horizontal  plane  and  in 
the  line  of  its  intersection  by  the  extended  median  plane 
cannot  be  fixed  by  these  eyes  without  depression  of  the 
visual  axes  by  contraction  of  the  inferior  recti,  aided  by 
the  superior  obliques.  Under- test,  either  one  of  these 
eyes  not  under  control  of  the  guiding  sensation  will  turn 
up  into  the  position  of  muscle  equilibrium,  showing-  a 
double  hyperphoria. 

In  the  study  of  all  these  figures,  all  of  the  muscles  are 
supposed  to  be  normal  in  development,  correct  in  attach- 
ment, and  perfectly  innervated.  A  hyperphoria,  single 
or  double;  a  cataphoria,  single  or  double;  a  h}rperphoria 
of  one  eye  and  a  cataphoria  of  the  other,  having  mal- 
formations of  the  orbits  as  the  sole  causative  agent, 
will  not  have  a  complicating  cyclophoria;  nor  can  any 
kind  of  malformation  of  the  orbits  ever  cause  c\rclo- 
phoria.  It  has  already  been  shown  that  orbits  that  are 
too  wide  apart  cause  exophoria,  while  orbits  that  are  too 
close  to  each  other  will  cause  esophoria. 


348        HYPERPHORIA  AXD  CATAPHORIA. 

It  should  be  remembered  that  other  causes  of  hyper- 
phoria  and  cataphoria  may  exist  when  e}Tes  are  set  in 
malformed  orbits,  and  that  the  other  causes  may  show 
themselves  in  an  increase  of  the  error  caused  by  the  mal- 
formation of  the  orbit,  or  ma}7  neutralize  it,  or  may  even 
reverse  it.  To  illustrate:  the  right  orbit  may  be  nor- 
mal, the  contained  eye  having-  its  vertical  and  transverse 
axes  properly  related  to  the  median  and  horizontal  fixed 
planes  of  the  head;  while  the  left  orbit  may  be  too  low, 
so  that  the  contained  eye  has  its  transverse  axis  below 
the  horizontal  plane  of  the  head  (see  Fig.  43).  As  a  con- 
sequence, the  muscles  being  well  balanced,  there  will  be 
a  left  cataphoria;  but  if  the  left  superior  rectus  is  too 
strong  for  its  opposing  inferior  rectus,  the  cataphoria  of 
orbital  causation  either  will  be  neutralized  or  there  will 
be  a  left  hyperphoria. 

When  malformation  of  the  orbits  is  the  only  cause  for 
vertical  imbalances,  the  resulting  errors  may  be  said  to 
be  pseudo-h}-perphoria  and  pseudo-cataphoria.  The 
treatment  of  such  errors  should  be  by  means  of  prisms 
in  positions  of  rest,  of  such  strength  as  to  fully  correct 
the  errors. 

There  is  no  direct  connection  between  the  brain-center 
for  the  ciliary  muscles  and  those  centers  controlling  the 
muscles  that  elevate  and  depress  the  eyes;  so  that, 
through  these  muscles,  a  focal  error  cannot  cause  a 


HYPERPHORIA  AND  CATAPHORIA.        349 

hyperphoria  or  a  cataphoria.  It  cannot  be  denied,  how- 
ever, that  convex  lenses  given  to  correct  hyperopia, 
sometimes  cure  a  hyperphoria  or  a  cataphoria.  Such 
cases  have  always  had  a  pseudo-esophoria  which,  like- 
wise, was  cured  by  the  convex  lenses.  It  is  clear  that 
in  such  cases  one  internus  is  attached  too  high  or  the 
other  internus  is  attached  too  low,  so  that  the  one  eye, 
on  being1  turned  in,  is  also  turned  up;  while  the  other 
eye,  on  being  turned  in,  is  also  turned  down.  The  same 
agent  (convex  lenses)  that  relieved  the  in-turning  (pseudo- 
esophoria)  relieved  also  the  up-turning  (pseudo-hyper- 
phoria)  and  the  down-turning  (pseudo-cataphoria).  Both 
intern!  attached  too  high  would  give,  under  the  same 
conditions,  a  double  pseudo-hyperphoria;  while  both 
interni  attached  too  low  would  give  a  double  pseudo- 
cataphoria.  There  would  also  be  a  complicating  cyclo- 
phoria,  which  will  be  studied  more  fully  in  Chapter  VII. 

In  the  same  way  it  could  be  shown  how  a  pseudo-exo- 
phoria,  because  of  too  high  or  too  low  attachment  of  one 
or  both  externi,  might  cause  a  pseudo-hyperphoria  or 
cataphoria,  one  or  both,  or  either  in  the  double  form,  all 
of  which  would  be  relieved  by  concave  lenses. 

Hyperphoria  and  cataphoria,  in  the  great  majority  of 
cases,  are  intrinsic,  or  inherent,  in  character.  They  are 
never  pseudo  except  when  caused  by  pseudo-esophoria 
and  pseudo-exophoria,  or  malformed  orbits. 


350  HYPERPHORIA   AND   CATAPHORIA. 

The  cause  of  an  intrinsic  vertical  error  may  reside 
wholly  in  the  interni,  but  only  when  there  is  an  intrin- 
sic esophoria  or  an  intrinsic  exophoria.  In  such  cases  of 
esophoria  one  or  both  interni  are  attached  too  high,  or 
one  or  both  are  attached  too  low,  or  one  is  attached  too 
high  and  the  other  is  attached  too  low.  In  the  one,  the 
esophoria  would  cause  a  double  hyperphoria  and  a  minus 
cyclophoria;  in  the  second  case  the  esophoria  would  cause 
double  cataphoria  and  plus  cyclophoria;  and  in  the  last 
case  the  esophoria  in  one  eye  would  cause  a  hyperphoria 
and  a  minus  cyclophoria,  and  in  the  other  a  cataphoria 
and  a  plus  cyclophoria.  How  to  deal  with  such  interni 
has  been  pointed  out  in  the  chapter  on  esophoria. 

Intrinsic  exophoria,  in  which  the  externi  are  attached 
too  high,  will  cause  double  hyperphoria  and  plus  cyclo- 
phoria; if  both  interni  are  attached  too  low,  the  exophoria 
will  cause  double  cataphoria  and  minus  cyclophoria.  If 
one  internus  is  too  high  and  the  other  is  too  low,  the  exo- 
phoria of  the  former  would  cause  hyperphoria  and  plus 
cyclophoria;  the  exophoria  of  the  latter  would  cause  cat- 
aphoria and  minus  cyclophoria.  How  to  deal  with  the 
externi  in  such  cases  has  been  set  forth  in  the  chapter 
on  exophoria. 

Hyperphoria  and  cataphoria,  in  the  greater  number  of 
cases,  are  caused  by  imbalance  of  the  vertically-acting 
muscles — the  supervertors  and  subvertors,  which  are  the 


HYPERPHORIA   AND    CATAPHORlA.  351 

superior  recti  and  inferior  obliques  and  the  inferior  recti 
and  the  superior  obliques.  When  the  cause  is  either  in 
the  straight  or  oblique  supervertors  or  in  the  straight 
or  oblique  subvertors,  the  error  is  always  inherent,  and 
never  pseudo. 

DOUBLE  HYPERPHORIA. — This  condition  may  be 
caused  by  the  two  superior  recti  being  hyper-developed, 
or  by  a  subnormal  development  of  the  inferior  recti;  or 
it  may  be  caused  by  the  superior  recti  having  their  at- 
tachments too  near  the  corneo-scleral  junction,  or  by  the 
inferior  recti  having  their  attachments  too  far  removed 
from  the  corneo-scleral  junction;  or  it  may  be  that  the 
first  conjugate  innervation  center  is  normally  so  endowed 
as  to  send  a  more  powerful  impulse  to  the  superior 
recti  than  goes  to  the  inferior  recti  from  the  second  con- 
jugate innervation  center.  If  either  of  these  conditions 
is  the  cause  of  a  double  hyperphoria,  there  will  also  be  a 
minus  cyclophoria,  independent  of  any  imbalance  of  the 
obliques. 

The  superior  and  inferior  recti  may  be  well  balanced, 
and  the  externi  and  interni  may  have  ideal  attachments, 
and  yet  there  may  be  a  double  hyperphoria.  The  cause 
would  be  found  in  imbalance  of  the  obliques,  the  inferior 
having  the.  advantage  over  the  superior,  either  because 
the  former  are  more  highly  developed  or  because  they 
are  attached  nearer  the  posterior  pole  or  because  the 


352  HYPERPHORIA   AND   CATAPHORIA. 

seventh  conjugate  innervation  impulse  is  more  intense 
than  that  from  the  sixth  conjugate  innervation  center. 
In  either  case  the  double  hyperphoria  would  be  asso- 
ciated with  plus  cyclophoria. 

In  double  hyperphoria  caused  by  the  superior  recti 
being  too  strong,  the  nervous  tension  of  the  inferior 
recti  would  counteract  both  the  hyperphoria  and  the 
minus  cyclophoria,  while  nervous  tension  of  the  superior 
obliques  would  help  to  counteract  the  hyperphoria,  but 
would  augment  the  minus  cyclophoria.  It  is  reasonable, 
therefore,  to  conclude  that  the  counteracting  nerve  im- 
pulse in  such  a  case  is  sent  only  to  the  inferior  recti. 
Depressing  the  chin — a  downcast  face — would  help  re- 
lieve the  inferior  recti  of  nervous  tension. 

In  double  hyperphoria  caused  by  the  inferior  obliques 
being  too  strong,  nervous  tension  of  the  superior  ob- 
liques would  counteract  both  the  hyperphoria  and  the 
plus  cyclophoria,  while  nervous  tension  of  the  inferior 
recti  would  help  to  counteract  the  hyperphoria,  but 
would  increase  the  plus  cyclophoria;  hence  the  conclu- 
sion that  the  counteracting  impulse,  in  such  a  case,  is 
sent  only  to  the  superior  obliques. 

Such  a  patient  would  instinctively  elevate  the  chin — 
carry  a  high  head — to  relieve  the  nervous. tension  of 
the  superior  obliques.  The  most  advantageous  posi- 
tion of  the  eyes  for  the  in-torting  action  of  the  superior 


HYPERPHORIA    AND    CATAPHORIA.  353 

obliques  is  a  depression  of  the  visual  axes  below  the 
fixed  horizontal  plane  of  the  head;  the  greater  this 
depression  of  the  visual  axes  (elevation  of  the  head), 
the  more  powerful  the  in-torting-  action  of  the  superior 
obliques. 

DOUBLE  CATAPHORIA. — This  condition  may  be  the 
result  of  hyper-development  of  the  inferior  recti  or  sub- 
normal development  of  the  superior  recti,  or  it  may 
result  from  the  inferior  recti  having-  their  attachment 
too  far  forward  or  from  the  superior  recti  being"  at- 
tached too  far  back;  or  it  may  be  caused  by  a  more  pow- 
ful  impulse  sent  from  the  second  con  jug-ate  innervation 
center  to  the  inferior  recti  than  is  generated  by  the  first 
conjug-ate  center  for  the  superior  recti.  In  either  case 
the  double  cataphoria  will  be  associated  with  plus  cyclo- 
phoria.  Nervous  tension  of  the  superior  recti  will  coun- 
teract both  the  cataphoria  and  the  plus  cyclophoria; 
while  nervous  tension  of  the  inferior  obliques  would 
counteract  the  cataphoria,  but  would  increase  the  plus 
cyclophoria.  Hence,  in  cases  like  the  above,  the  correct- 
ive nerve  impulse  must  be  sent  only  to  the  superior 
recti.  The  position  of  the  eyes  most  favorable  for  ef- 
fective action  of  the  superior  recti  is  a  depression  of  the 
visual  axes  below  the  horizontal  plane  of  the  head;  hence 
such  patients  will  carry  their  heads  hig"h,  so  as  to  lessen 
the  nervous  tension  of  the  superior  recti. 


354        HYPERPHORIA  AND  CATAPHORIA. 

Double  cataphoria  may  be  caused  by  imbalance  of  the 
obliques,  the  superior  being  stronger  than  the  inferior, 
either  because  the  former  are  hyper-developed  or  the  lat- 
ter are  subnormally  developed,  or  because  the  former  are 
attached  nearer  the  posterior  pole,  or  because  the  sixth 
conjugate  innervation  is  more  powerful  than  the  seventh. 
In  either  case  the  double  cataphoria  would  be  associated 
with  minus  cyclophoria.  The  corrective  nerve  impulse 
would  be  sent  to  the  inferior  obliques,  which  would  coun- 
teract both  the  double  cataphoria  and  the  minus  cyclo- 
phoria. The  position  of  the  eyes  most  favorable  for  cor- 
rective action  of  the  inferior  obliques  is  an  elevation  of 
the  visual  axes  above  the  extended  horizontal  plane  of 
the  head;  hence  such  patients  would  have  their  faces 
downcast,  for  this  pose  of  the  head  would  help  to  relieve 
the  nervous  tension  of  the  inferior  obliques. 

Hyperphoria  of  one  eye  and  cataphoria  of  the  other, 
independent  of  malformation  of  the  orbits  and  faulty 
attachments  of  the  lateral  recti  muscles,  are  always  in- 
herent in  the  vertically-acting  muscles,  and  never  inner- 
vational.  For  convenience  of  study  the  right  eye  will  be 
considered  as  hyperphoric  and  the  left  eye  as  cataphoric, 
although  the  reverse  is  often  found.  The  right  hyper- 
phoria  is  due  to  the  fact  that  the  superior  rectus  is  too 
strong  for  its  direct  antagonist,  the  inferior  rectus,  or 
that  the  inferior  oblique  is  too  strong  for  the  superior 


HYPERPHORIA   AND    CATAPHORIA.  355 

oblique;  or  both  of  these  conditions  may  unite  in  the  de- 
velopment of  the  hyperphoria.  If  the  superior  rectus 
alone  is  the  cause  of  the  hyperphoria,  it  is  because 
this  muscle  is  hyper -developed  or  that  the  inferior 
rectus  is  of  subnormal  development,  or  that  the  supe- 
rior rectus  is  attached  too  near  the  cornea  or  that  the 
attachment  of  the  inferior  rectus  is  too  far  removed  from 
the  cornea. 

The  hyperphoria  would  be  sthenic  if  the  superior  rectus 
is  hyper-developed  or  is  attached  too  near  the  cornea;  it 
would  be  asthenic  if  the  inferior  rectus  is  subnormally 
developed  or  is  attached  too  far  away  from  the  cornea. 
In  either  case  the  hyperphoria  would  manifest  itself  in 
association  with  minus  cyclophoria. 

If  the  inferior  oblique  alone  is  the  cause  of  the  hyper- 
phoria, it  is  because  of  hyper-development  of  this  muscle 
or  a  subnormal  development  of  the  superior  oblique;  or 
because  the  inferior  oblique  is  attached  too  far  behind 
the  equator  or  the  superior  oblique  is  attached  too  near 
the  equator.  The  hyperphoria  thus  caused  is  sthenic  in 
cases  in  which  the  inferior  oblique  is  hyper-developed  or 
is  attached  too  far  behind  the  equator;  it  is  asthenic  in 
those  cases  in  which  the  superior  oblique  is  subnormally 
developed  or  is  attached  too  close  to  the  equator.  In 
either  condition  the  hyperphoria  would  show  itself  in 
association  with  plus  cyclophoria. 


356  HYPERPHORIA   AND    CATAPHORIA. 

When  the  hyperphoria  manifests  itself  unassociated 
with  either  minus  or  plus  cyclophoria,  it  becomes  evident 
that  both  the  superior  rectus  and  inferior  oblique  enter 
into  the  causation. 

The  left  eye  under  test  will  show  cataphoria,  usually 
the  same  in  quantity  as  the  hyperphoria  of  the  right 
eye.  The  cataphoria  is  caused  by  either  a  too  powerful 
inferior  rectus  or  a  too  powerful  superior  oblique;  or 
both  of  these  muscles  ma}T  unite  in  the  production  of  the 
cataphoria. 

In  a  case  in  which  the  inferior  rectus  alone  is  the 
causative  agent,  it  is  either  hyper-developed  or  has  its  at- 
tachment too  close  to  the  cornea;  or  its  direct  antagonist, 
the  superior  rectus,  is  subnormally  developed  or  is  at- 
tached too  far  away  from  the  cornea.  The  cataphoria 
would  be  sthenic  if  the  inferior  rectus  is  either  hyper- 
developed  or  is  attached  too  near  the  cornea;  it  would 
be  asthenic  if  the  superior  rectus  is  under-developed  or 
has  its  attachment  too  far  removed  from  the  cornea.  In 
either  case  the  cataphoria  would  be  associated  with  a 
plus  cyclophoria. 

In  a  case  in  which  the  superior  oblique  is  the  sole 
cause  of  the  cataphoria,  it  is  either  because  it  is  hyper- 
developed  or  because  it  has  its  attachment  too  near  the 
posterior  pole;  or  because  its  direct  antagonist,  the  in- 
ferior oblique,  is  subnormally  developed  or  is  attached 


HYPERPHORIA   AND   CATAPHORIA.  357 

too  near  the  equator.  The  resulting-  cataphoria  is  sthenic 
in  those  cases  in  which  the  superior  oblique  is  either 
hyper-developed  or  is  attached  too  near  the  posterior 
pole;  it  is  asthenic  when  the  inferior  oblique  is  under- 
developed or  is  attached  too  near  the  equator.  In  either 
case  the  cataphoria  would  be  associated  with  a  minus 
cyclophoria.  Cataphoria  will  be  unassociated  with  either 
plus  or  minus  cyclophoria  only  when  both  the  inferior 
rectus  and  superior  oblique  are  united  in  the  causation. 

Nervous  tension  of  the  inferior  rectus  counteracts  the 
rig-ht  hyperphoria,  if  caused  by  the  superior  rectus; 
while  nervous  tension  of  the  superior  rectus  will  coun- 
teract the  left  cataphoria,  if  caused  by  the  inferior 
rectus.  Not  only  will  the  right  hyperphoria  and  left 
cataphoria  be  thus  neutralized,  but  the  minus  cyclopho- 
ria of  the  rig-ht  and  plus  c}7clophoria  of  the  left  would 
be  suppressed  by  the  nervous  tension  of  the  same 
muscles.  The  corrective  impulse  would  come  not  from 
one  conjugate  center,  as  in  double  hyperphoria  and 
double  cataphoria,  but  from  two  separate  centers. 

Nervous  tension  of  the  superior  oblique  counteracts 
the  rig-ht  hyperphoria  which  is  caused  by  the  inferior 
oblique,  while  nervous  tension  of  the  inferior  oblique 
will  counteract  the  left  cataphoria  that  is  caused  by  the 
superior  oblique.  The  plus  cyclophoria  of  the  right  eye 
and  the  minus  cyclophoria  of  the  left  eye  will  be  sup- 


358        HYPERPHORIA  AND  CATAPHORIA. 

pressed  by  the  nervous  tension  of  the  same  muscles  that 
counteract  the  hyperphoria  and  cataphoria. 

TESTS. 

The  phorometer,  with  perfectly  ad-justed  prisms  and 
spirit  level,  alone  can  be  depended  on  in  testing  for 
hyperphoria  and  cataphoria.  The  slightest  error  in 
testing  will  be  followed  by  bad  results  in  practice.  In 
attempting  to  test  for  these  errors  by  means  of  a  dis- 
placing prism  with  its  axis  horizontal,  held  in  the  hand, 
one  would  have  to  be  very  careful  or  the  axis  would  be 
slightly  inclined  in  one  direction  or  the  other;  so  that,  if 
the  eye  under  test  is  hyperphoric  and  the  temporal  end 
of  the  prism  inclines  down,  the  error  will  be  exagger- 
ated, and  if  it  inclines  upward,  the  hyperphoria  would 
be  neutralized  more  or  less  completely,  or  even  a  cata- 
phoria might  be  shown. 

For  reasons  already  given  the  rod  test  is  not  to  be 
trusted  implicitly,  but  it  is  much  to  be  preferred  over 
the  hand-prism  test,  or  even  the  prism  when  set  in  the 
trial  frame  of  the  refraction  case.  The  test  object  being 
a  candle,  a  rod  held  with  its  axis  vertical  before  one  eye 
will  show  the  streak  of  light  which,  in  orthophoria, 
should  pass  directly  through  the  blaze  seen  by  the  other 
eye;  in  hyperphoria,  the  streak  would  pass  below  the 
blaze,  while  in  cataphoria  it  would  pass  above  the  blaze. 


HYPERPHORIA    AND    CATAPHORIA.  359 

In  the  low  degrees  of  vertical  heterophoria,  the  streak 
falling-  on  the  area  of  binocular  fusion  will  excite  some 
effort,  however  small,  at  fusion.  In  the  higher  errors, 
the  prism  used  for  measuring  the  amount  of  the  error, 
by  throwing  the  streak  on  the  fusion  area,  would  excite 
some  effort  at  fusion.  When  the  rod  is  the  means  of 
testing,  the  error  is  never  shown  in  excess,  and  for  this 
reason  is  more  safe  than  accurate. 

The  use  of  the  plus  13  D  lens  before  one  eye,  if  not 
worthy  of  trust  in  the  examinations  for  esophoria  and 
exophoria,  would  certainly  be  less  trustworthy  in  exami- 
nations for  hyperphoria  and  cataphoria. 

In  high  degrees  of  a  vertical  error  the  plane  red  glass 
held  before  one  eye  will  cause  diplopia,  the  red  light 
below  in  hyperphoria  and  above  in  cataphoria.  When 
the  red  image  is  entirely  outside  the  area  of  binocular 
fusion,  the  full  error  will  be  shown,  but  cannot  be  accu- 
rately measured,  for  the  reason  that  the  rotary  or  other 
prism  that  carries  the  red  image  into  the  fusion  area,  at 
once  excites  some  effort  at  fusion.  Like  the  rod  test, 
the  red-glass  test  will  mislead  only  in  that  it  will  not 
show,  even  on  careful  measurement,  the  full  error. 

The  cover  test  will  show  the  vertical  errors,  but  no  one 
would  think  of  basing  the  treatment  of  a  case  on  this  test. 

Any  of  the  standard  phorometers  may  be  used  in  test- 
ing for  vertical  heterophoria,  but  in  this  the  monocular 


360        HYPERPHORIA  AND  CATAPHORIA. 

instrument  is  most  useful  and  trustworthy.  The  10° 
prism,  base  in,  should  be  placed  in  the  cell  behind  the 
rotary  prism;  the  controlling-  screw  should  be  vertical, 
and  the  index  should  stand  at  zero.  The  instrument 
should  be  perfectly  level.  The  patient's  head  should  be 
in  the  primary  position.  The  test  object  should  be,a 
white  spot  on  a  black  background,  and  should  be  distant 
twenty  feet.  With  the  instrument  before  the  right  eye 
there  will  appear  to  be  two  spots,  the  true  one  to  the 
left  and  the  false  one  to  the  right.  If  they  are  too 
widely  separated,  as  in  cases  that  are  esophoric,  the  6° 
prism  should  be  substituted  for  the  10°  prism.  The 
patient  should  constantly  fix  the  true  spot,  and  by  indirect 
vision  alone  should  locate  and  relate  the  false  spot.  If 
the  eye  is  hyperphoric,  the  false  spot  will  be  lower  than  the 
true;  and  since  its  image  is  not  on -the  area  of  binocular 
fusion,  the  full  error  will  be  shown.  The  index  of  the 
rotary  prism  moved  upward  \vill  accurately  measure  the 
error;  for  in  carrying  the  false  object  up  to  the  level  of 
the  true,  the  image  of  the  former  is  not  made  to  invade 
the  fusion  area,  provided  the  true  object  alone  has  been 
fixed  throughout  the  test. 

The  vertical  imbalance  of  one  eye  having  been  taken, 
the  phorometer  should  be  turned  in  front  of  the  other. 
Precisely  the  same  steps  should  be  taken  in  determining 
the  condition  of  its  vertically-acting  muscles.  Hyper- 


HYPERPHORIA  AND  CATAPHORIA.        361 

phoria  having  been  found  in  the  eye  first  tested,  the  fel- 
low eye,  as  a  rule,  will  be  found  cataphoric.  The  false 
object  will  appear  higher  than  the  true.  The  index  of 
the  rotary  prism  should  be  carried  downward  until  the 
false  object  reaches  a  level  with  the  true  object.  The 
quantity  of  the  error,  as  indicated  on  the  scale,  should 
be  noted.  In  the  greater  number  of  cases  the  degree  of 
cataphoria  will  be  the  same  as  the  hyperphoria  of  the 
other  eye. 

One  eye  having  shown  hyperphoria,  the  other  may 
show  vertical  orthophoria  or  even  hyperphoria.  The 
eye  under  test,  seeing  the  false  object  by  indirect  vision, 
does  not  receive  any  fusion  stimulus;  hence  it  always 
turns  into  the  position  of  equilibrium  of  all  its  muscles. 
For  this  reason  it  is  just  as  easy  to  determine  the  exist- 
ence of  a  double  hyperphoria,  with  the  monocular  pho- 
rometer,  as  it  is  to  ascertain  the  existence  of  any  other 
form  of  heterophoria.  The  patient  must  be  impressed 
with  the  absolute  importance  of  always  fixing-  the  true 
object — that  is,  must  see  it  by  direct  vision. 

Whether  one  or  the  other  of  the  tests  referred  to 
above  should  be  adopted,  the  proof  test  for  vertical  im- 
balance should  not  be  neglected.  Errors  that  may  have 
crept  in  because  of  carelessness  of  the  operator  or  indif- 
ference of  the  patient  can  be  eliminated  easily  by  the 
proof  test.  The  means  of  -proving-  is  the  Maddox  double 


362        HYPERPHORIA  AND  CATAPHORIA. 

prism  (4°  to  6°  each).  This  should  be  held  in  the  hand 
first  before  one  eye  and  then  the  other,  so  that  the  line 
of  union  of  the  prism  bases  shall  be  horizontal.  The 
fixing1  eye  should  be  the  one  not  under  test.  The  prism 
should  be  moved  up  and  down  before  the  eye  under  test, 
so  that  one  moment  the  false  object  would  be  seen  below 
the  true  and  the  next  moment  above  it,  but  always  by 
indirect  vision.  If  the  distance  from  the  true  to  the 
false  object  is  the  same  when  below  as  it  is  when  above, 
there  is  vertical  orthophoria.  If  there  is  hyperphoria, 
the  false  object,  when  seen  through  the  upper  prism, 
will  be  closer  to  the  true  object,  by  twice  the  amount  of 
the  error,  than  when  seen  through  the  lower;  while  the 
reverse  will  be  true  if  there  is  cataphoria.  In  double 
hyperphoria  the  objects  will  be  closer  together  for  each 
eye  when  the  false  object  is  seen  through  the  upper 
prism;  while  in  double  cataphoria  the  false  object,  when 
seen  through  the  lower  prism  by  each  eye,  will  be  nearer 
the  true  object  than  when  seen  through  the  upper 
prism.  If  there  is  hyperphoria  of  one  eye  and  catapho- 
ria of  the  other,  when  the  double-prism  proof  test  is 
applied  to  the  hyperphoric  eye,  the  false  object  seen 
through  the  upper  prism  will  be  close  to  the  true,  and 
will  be  farther  removed  from  it  when  seen  through  the 
lower  prism.  On  shifting  the  test  to  the  other  eye,  the 
false  object  seen  through  the  lower  prism  will  be  nearer 


HYPERPHORIA   AND   CATAPHORIA.  363 

the  true  than  when  it  is  seen  through  the  upper  prism. 
The  double  prisms  should  be  of  equal  strength,  and 
each  should  be  strong-  enough  to  throw  the  image  of  the 
test  object  entirely  above  or  below  the  limits  of  the  field 
of  fusion. 

Dr.  Doak,  Assistant  in  Ophthalmology,  Vanderbilt 
University,  has  devised  a  test  for  vertical  imbalances 
that  not  only  detects  and  measures  the  error,  but  is  also 
in  itself  a  proof  test.  By  this  test  the  kind  of  error  is 
at  once  detected,  but  its  quantity  is  not  known  until  the 
proof  feature  has  been  applied.  The  delicacy  of  the 
test  is  shown  by  an  apparent  doubling  of  the  quantity 
of  the  error.  This  delicacy  makes  it  dangerous  only 
when  the  operator  forgets  that  the  apparent  error  is 
twice  that  of  the  real  error.  For  making  this  test  the 
monocular  phorometer  must  be  placed  before  one  eye, 
and  in  the  cell  next  to  the  eye  must  be  placed  either  the 
10°  or  6°  prism,  base  toward  the  nose.  The  controlling 
screw  must  be  vertical,  and  the  index,  at  the  beginning, 
should  stand  at  zero.  The  instrument  must  be  level. 
The  patient  must  hold  before  the  other  eye  a  double 
prism  in  such  position  as  to  make  the  test  object  (white 
spot  on  a  black  background)  double  for  that  eye,  the 
one  directly  above  the  other,  and  the  two  should  be  12° 
apart — that  is,  each  of  the  double  prisms  should  be  6°. 
With  the  double  prism  thus  adjusted,  these  two  spots 


364  HYPERPHORIA   AND   CATAPHORIA. 

must  be  seen  by  indirect  vision,  while  the  single  spot  seen 
by  the  other  eye  should  be  observed  by  direct  vision. 
Because  of  the  displacing  prism  behind  the  phorometer, 
the  single  object  will  not  be  in  line  with  the  other  two; 
and  when  it  is  seen  by  direct  vision,  the  other  eye  will 
be  so  turned  that  the  vertical  imaginary  line  connecting 
the  two  false  objects  will  fall  to  the  nasal  side  of  the 
fusion  area,  so  that,  as  the  test  proceeds,  there  will  be 
made  no  effort  at  fusion.  The  eye  behind  the  double 
prism  will  be  wholly  off  its  guard.  The  moment  the 
single  object  is  fixed,  the  patient  can  usually  say  whether 
or  not  it  would  be  halfway  between  the  other  two  ob- 
jects if  it  were  in  line  with  them.  If  the  middle  object 
is  seen  nearer  the  lower,  that  eye  is  hyperphoric;  if 
nearer  the  upper,  it  is  cataphoric.  The  proof  feature  of 
the  test  results  from  the  use  of  the  rotary  prism.  When 
the  screw  is  turned  so  as  to  carry  the  index  upward,  the 
patient  is  asked  to  speak  the  moment  the  single  object  is 
in  a  horizontal  line  with  the  upper  of  the  two  false  ob- 
jects. The  extent  of  the  rotation  is  noted,  after  which 
the  rotary  prism  is  again  made  neutral.  The  next  step 
is  to  carry  the  index  of  the  rotary  prism  downward  until 
the  patient  says  that  the  single  object  is  in  a  horizontal 
line  with  the  lower  of  the  two  false  objects.  The  extent 
of  downward  rotation  is  now  noted.  If  the  two  arcs 
traversed  by  the  index  are  equal,  there  is  undoubtedly 


HYPERPHORIA    AND   CATAPHORIA.  365 

vertical  orthophoria  of  this  eye.  If  the  lower  arc  is  5° 
and  the  upper  arc  is  7°,  this  eye  is  certainly  hyperphoric— 
not  to  the  extent  of  the  difference  between  these  two 
arcs,  which  would  be  2°,  but  only  half  this  amount — viz., 
1°.  If  the  upper  arc  is  5°  and  the  lower  arc  is  7°,  there  is 
cataphoria — not  of  2°,  but  of  1°.  The  reason  for  saying 
that  the  real  vertical  error  is  only  one-half  of  the  appar- 
ent error  is  clear.  Since  each  of  the  double  prisms  is 
6°,  the  double  objects  seen  through  them,  \vhen  the  base- 
line is  in  the  extended  horizontal  plane  of  the  head,  are 
12°  apart.  The  extended  horizontal  plane  of  the  head 
cuts  the  imaginary  line  connecting  the  two  false  objects 
at  the  midway  point — 6°  from  each.  If  the  displaced  ob- 
ject seen  by  direct  vision  with  the  other  eye  is  in  this 
plane,  it  would  have  to  be  carried  up  or  down  by  the 
rotary  prism  just  6°  to  be  placed  in  a  horizontal  line 
with  the  one  or  the  other  of  the  false  objects,  hence  the 
eye  would  be  orthophoric  vertically.  If  the  true  object 
is  1°  below  the  extended  horizontal  plane  of  the  head,  it 
will  have  to  be  carried  downward  by  the  rotary  prism 
only  5°  to  be  placed  in  a  horizontal  line  with  the  lower 
object,  while  it  would  have  to  be  carried  upward  7°  to 
stand  in  a  horizontal  line  with  the  upper  object.  Thus 
it  is  clear  that  the  hyperphoria  shown  by  this  test  is 
one-half  the  difference  between  the  arcs  traversed  by  the 
index  of  the  phorometer  in  placing  the  true  object  in  a 


366  HYPERPHORIA    AND   CATAPHORIA. 

horizontal  line  first  with  the  one  false  object  and  then 
with  the  other,  the  index  each  time  starting  from  zero. 
Throughout  the  entire  test  the  single  object  must  be 
fixed.  Although  this  test  is  in  a  sense  binocular,  it  is 
probably  better  than  any  other  test  for  two  reasons:  (a) 
It  doubles  the  real  error,  so  that  a  small  error  will  be  less 
likely  to  be  overlooked;  (b)  this  test  proves  itself. 

The  eye  under  the  Doak  test  is  the  one  behind  the 
rotary  prism.  Both  eyes"  should  be  subjected  to  the  same 
test. 

The  duction  and  version  power  of  the  superior  and  in- 
ferior recti  of  both  eyes  must  be  taken  in  order  to  deter- 
mine whether  the  hyperphoria  and  cataphoria  are  sthenic 
or  asthenic,  for  on  this  knowlege  must  depend  the  treat- 
ment of  the  case. 

If  the  superduction  is  less  than  3°  and  the  superver- 
sion  is  33°  or  less,  the  hyperphoria  is  asthenic;  if  sub- 
duction  is  less  than  3°  and  sub-version  is  below  50°,  the 
cataphoria  is  asthenic.  If  superduction  is  more  than  3° 
and  superversion  is  greater  than  33°,  the  hyperphoria  is 
sthenic;  if  sub-duction  is  more  than  3°  and  sub-version  is 
greater  than  50°,  the  cataphoria  is  sthenic. 

COMPLICATIONS. — Focal  errors  do  not  complicate  ver- 
tical heterophorias,  except  in  cases  in  which  there  is 
pseudo-esophoria  or  pseudo-exophoria  with  too  high  or 
too  low  attachments  of  the  lateral  recti  muscles.  A 


HYPERPHORIA  AND  CATAPHORIA.         367 

vertical  error  thus  caused  is  pseudo  in  character  and  is 
cured,  as  is  also  the  lateral  pseudo-error,  by  correction 
of  the  focal  errors. 

The  only  complication  that  must  always  be  thought  of 
in  the  study  of  hyperphoria  and  cataphoria  is  cyclopho- 
ria;  for  by  this  complication  is  determined  the  treatment, 
surgical  or  otherwise,  of  these  errors.  How  to  find  and 
measure  this  all-important  complication  will  be  set  forth 
;.n  the  next  chapter.  If  a  hyperphoria  is  only  complicated 
by  esophoria  or  exophoria  or  by  any  focal  error,  all  these 
troubles  must  be  treated  as  if  they  existed  alone. 

SYMPTOMS. 

Any  and  all  of  the  symptoms  mentioned  in  the  chapter 
on  heterophoria  may  be  caused  by  vertical  imbalance. 
There  is  no  facial  expression  that  can  be  dignified  as 
diagnostic  of  hyperphoria  and  cataphoria.  There  are 
poses  of  the  head  peculiar  to  both  double  hyperphoria 
and  double  cataphoria.  High-headedness  is  a  symptom 
of  double  hyperphoria  when  the  inferior  obliques  cause 
the  error,  and  is  just  as  certainly  a  sign  of  double  cata- 
phoria when  the  inferior  recti  are  the  cause  of  the  error. 
The  most  favorable  position  of  the  eyes  for  effective  ac- 
tion of  weak  superior  obliques  and  weak  superior  recti 
under  a  corrective  nerve  impulse  is  a  depression  of  the 
visual  axes  below  the  extended  horizontal  plane  of  the 


368        HYPERPHORIA  AND  CATAPHORIA. 

head,  or  (what  is  the  same  thing")  elevation  of  the  ex- 
tended horizontal  plane  of  the  head. 

The  downcast  look  is  a  sign  of  double  hyperphoria 
when  the  error  is  caused  by  the  superior  recti,  and  of 
double  cataphoria  when  the  error  is  caused  by  the  supe- 
rior obliques. 

The  most  favorable  position  of  the  eyes  for  effective 
action  of  weak  inferior  obliques  and  weak  inferior  recti, 
under  a  corrective  nervous  impulse,  is  an  elevation  of  the 
visual  axes  above  the  extended  horizontal  plane  of  the 
head,  or  (what  is  equal  to  it)  a  depression  of  the  hori- 
zontal plane  of  the  head. 

A  tilting-  of  the  head  toward  one  shoulder  or  the  other 
occurs  only  in  cases  in  which  there  is  a  hyperphoria  of 
one  eye  and  a  cataphoria  of  the  other,  complicated  by 
either  plus  or  minus  cyclophoria  of  both  eyes,  and  never 
in  simple  cases  of  hyperphoria.  The  hyperphoria  and 
cataphoria  are  not  the  cause  of  the  tilting-  of  the  head; 
the  cause  is  the  complicating-  cyclophoria.  If  the  com- 
plication is  plus  cyclophoria,  the  head  will  be  tilted 
toward  the  cataphoric  side.  In  a  case  of  this  kind,  tilt- 
ing the  head  elevates  the  hyperphoric  eye  and  depresses 
the  cataphoric  eye;  so  that  to  fix  an  object  that  would 
be  in  the  extended  horizontal  plane  of  the  head,  if  the 
head  were  erect,  makes  it  necessary  that  the  visual  axis 
of  the  eye  that  is  higher  shall  be  depressed  and  that  the 


HYPERPHORIA  AND  CATAPHORIA.        369 

visual  axis  of  the  eye  that  is  lower  shall  be  elevated,  so 
as  to  make  them  intersect  at  the  object.  Depression  of 
the  visual  axis  of  the  hyperphoric  eye  places  the  eye  in 
such  a  position  (elevated  posterior  pole)  as  to  g-ive  to  the 
superior  oblique,  under  the  whole  of  the  stimulus  of  the 
sixth  fusional  innervation,  its  greatest  torsioning-  power, 
which  would  enable  it  easily  to  parallel  the  vertical  axis 
of  the  eye  with  the  now-inclined  median  plane  of  the 
head.  The  hyperphoria  in  such  a  case  is  due  largely 
to  the  inferior  oblique,  and  the  plus  cyclophoria  is 
wholly  caused  by  it.  The  elevated  posterior  pole  of 
the  eye,  made  necessary  by  the  tilting1  of  the  head, 
places  the  inferior  oblique  at  a  disadvantage  to  the 
weak  superior  oblique;  hence,  the  greater  ease  with 
which  both  the  hyperphoria  and  the  plus  cyclophoria 
are  counteracted. 

The  cataphoria  of  the  other  eye  must  be  caused  by  the 
inferior  rectus,  and  the  same  muscle  most  probably  causes 
the  whole  of  the  plus  cyclophoria  of  this  eve.  The  cor- 
rective stimulus  most  likely  conies  from  the  first  fu- 
sional innervation  center  and  is  wholl}r  expended  on 
the  superior  rectus  of  the  cataphoric  eye  (none  of  it  is 
needed  for  the  superior  rectus  of  the  hyperphoric  eye), 
enabling-  it  to  counteract  both  the  cataphoria  and  the 
plus  cyclophoria.  Its  action  is  not  favored  by  posi- 
tion. A  corrective  stimulus  sent  to  the  superior  oblique 


370        HYPERPHORIA  AND  CATAPHORIA. 

would  lessen  the  cyclophoria,  but  increase  the  cata- 
phoria;  therefore  it  is  reasonable  to  conclude  that  none 
is  sent  to  it. 

In  a  case  of  hyperphoria  of  one  eye  and  cataphoria  of 
the  other,  complicated  by  a  minus  cyclophoria,  the  head 
is  tilted  toward  the  hyperphoric  side.  The  cataphoric 
eye  is  elevated,  the  hyperphoric  eye  is  depressed,  by  this 
position  of  the  head;  so  that  the  visual  axis  of  the  higher 
eye  must  be  depressed  and  that  of  the  lower  eye  must  be 
elevated,  so  as  to  intersect  at  a  point  that  would  be  in 
the  extended  horizontal  plane  of  the  head,  if  it  were 
erect.  In  this  case  the  hyperphoria  and  minus  cyclopho- 
ria must  be  due  to  the  superior  rectus  of  that  eye,  while 
the  cataphoria  and  the  minus  cyclophoria  of  the  other 
eye  must  be  due  to  its  superior  oblique.  The  corrective 
impulse  of  the  hyperphoria  must  be  sent  to  the  inferior 
rectus  which  is  favored  in  its  action  by  the  necessary 
elevated  position  of  its  visual  axis.  It  must  also  receive 
nearly  the  whole  of  the  impulse  that  comes  from  the 
second  fusional  innervation  center;  for  the  inferior 
rectus  of  the  other  eye  needs  but  little,  if  any,  of  it. 
Thus  are  counteracted  both  the  hyperphoria  and  the 
minus  cyclophoria. 

The  cataphoria  and  the  minus  cyclophoria  of  the  other 
eye  are  counteracted  by  a  corrective  nervous  impulse  that 
is  sent  to  its  inferior  oblique  whose  action  is  not  favored 


HYPERPHORIA  AND  CATAPHORIA.        371 

by  the  position  that  this  eye  must  assume — an  elevated 
posterior  pole. 

From  what  has  been  said  above  it  will  be  observed 
that  the  tilting-  of  the  head  toward  the  cataphoric  side 
when  there  is  plus  cyclophoria,  and  toward  the  hyper- 
phoric  side  when  there  is  minus  cyclophoria,  is  favorable 
only  to  the  muscle  that  must  correct  the  double  error  of 
the  hyperphoric  eye,  thus  showing-  that  the  depressor 
muscles  are  in  greater  need  of  the  help  that  comes  from 
posing.  The  tilting-  is  really  unfavorable  to  the  muscle 
that  must  correct  the  double  error  of  the  cataphoric  eye. 
It  may  be  that  a  nervous  impulse  gets  a  readier  response, 
in  unfavorable  positions  of  the  head,  from  the  muscles 
that  elevate  the  eyes  than  from  those  that  depress  them. 
It  is  well  known  that  when  the  eyes  are  closed  in  sleep, 
or  even  in  meditation,  they  turn  slightly  up;  and  the 
same  is  true  under  anesthesia  that  is  not  profound. 
This  peculiar  endowment  of  the  supervertors  seems  to 
be  necessary  in  order  that  the  cornea  may  be  carried 
instantly,  for  protection,  into  the  position  of  greatest 
security. 

It  is  doubtful  if  there  is  a  symptom  or  sign,  other  than 
the  posing  of  the  head,  that  is  peculiar  to  vertical  im- 
balance. Excessive  secretion  of  tears  may  be  associated, 
in  some  unaccountable  way,  with  hyperphoria  and  cata- 
phoria. 


372  HYPERPHORIA  AND  CATAPHORIA. 

TREATMENT. 

Vertical  imbalance  associated  with  pseudo-esophoria 
or  pseudo-exophoria  may  be  dependent  on  it;  and  if  so, 
it  should  be  relieved  by  the  same  lenses  that  cure  the 
lateral  pseudo  error. 

Since  a  double  hyperphoria  may  be  caused  by  abnormal 
action  of  the  inferior  obliques,  excited  by  oblique  astig- 
matism with  the  meridians  of  greatest  curvature  con- 
verging above,  and  since  double  cataphoria  may  be  caused 
by  abnormal  action  of  the  superior  obliques,  excited  by 
oblique  astigmatism  with  the  meridians  of  greatest  curv- 
ature diverging  above,  these  errors  may  be  relieved,  in 
such  cases,  by  the  correcting  plus  or  minus  cylinders. 

Inherent  vertical  imbalance  is  made  neither  better  nor 
worse  by  the  lenses  that  correct  focal  errors.  These 
must  be  treated  by  exercise,  by  prisms  in  positions  of 
rest,  or  by  operations. 

EXERCISE. 

Double  hyperphoria  may  be  treated  by  exercise  of  the 
inferior  recti,  which  is  best  done  by  looking  straight 
ahead  and  then  down  to  an  object  on  the  floor  five 
or  six  feet  distant,  then  again  straight  ahead  and 
then  down  again,  repeating  this  at  regular  intervals 
of  three,  seconds.  This  straight-forward-to-floor  exer- 
cise should  be  stopped  short  of  fatigue,  and  should  not  be 


HYPERPHORIA  AND  CATAPHORIA. 


373 


continued  longer  than  ten  minutes.  One  exercise  a  day 
is  sufficient. 

The  exercise  for  double  cataphoria  is  straight-forward- 
to-ceiling  exercise,  and  should  be  carried  out  in  the  same 
manner  as  the  straight-forward-to-floor  exercise. 

Prism  exercise  alone  is  applicable  when  there  is  hyper- 
phoria  of  one  eye  and  cataphoria  of  the  other.  The 


Fig-  47. 

prisms  with  which  to  begin  the  exercise  should  be  weak, 
and  gradually  stronger  ones  should  be  used,  but  they 
should  never  be  stronger  than  2°.  Except  for  the  cost, 
the  prisms  should  be  in  pairs  of  equal  strength.  The 
hyperphoric  set  shown  in  the  accompanying  cut  (Fig.  47) 
consists  of  five  prisms,  as  follows:  ?°,  5°,  1°,  l^0*  and  2°. 


374  HYPERPHORIA   AND   CATAPHORIA. 

The  apex  of  the  prism  must  point  toward  the  muscle  to 
be  exercised — that  is,  it  must  be  down  for  the  hyper- 
phoric  eye  and  up  for  the  cataphoric  eye.  When  the 
prisms  are  of  unequal  strength,  after  three  or  four  days' 
use  they  should  be  transferred  and  the  exercise  continued 
for  three  or  four  days  longer.  Now  the  weaker  prism 
(j°)  may  be  removed  and  the  1°  prism  put  in  its  place. 
At  the  proper  time  the  £°  prism  and  the  1°  prism  should 
be  transferred,  and  the  exercise  should  be  continued  with 
them  for  three  days,  when  the  2°  prism  should  be  re- 
moved and  the  l^0  prism  put  in  its  place.  The  substitu- 
tions should  thus  continue  until  the  1^°  and  2°  prisms 
are  in  the  frames.  The  exercise  should  be  continued 
indefinitely  with  these  prisms,  transferring-  them  from 
side  to  side  at  regular  intervals,  always  placing  apex 
down  for  the  hyperphoric  eye  and  apex  up  for  the  cata- 
phoric eye.  The  muscles  should  be  exercised  rhythmic- 
ally by  lowering  and  raising  the  frames  containing  the 
prisms,  at  intervals  of  three  seconds.  The  exercise  should 
be  stopped  short  of  fatigue  and  need  not  be  continued 
longer  than  ten  minutes.  Once  a  day  is  sufficiently  often 
to  exercise.  The  object  of  fixation  while  exercising 
should  be  twenty  feet  distant,  and  should  be  sufficiently 
sharp  in  outline  and  bright  to  excite  ready  response  of 
the  muscles  for  the  purpose  of  fusing  the  two  displaced 
images. 


HYPERPHORIA    AND   CATAPHORIA.  375 

Relieving-  prisms  for  vertical  imbalance  are  often  of 
great  use.  Hyperphoria  and  cataphoria,  uncompli- 
cated, of  less  than  1|°,  should  be  relieved,  if  possible, 
either  by  exercise  or  by  rest  prisms.  Cases  in  which 
these  errors  are  as  great  as  2°  or  greater,  whether 
complicated  or  not,  may  obtain  some  relief  from  non- 
surg-ical  means,  but  cannot  be  cured  short  of  operations. 
If  the  vertical  errors  are  as  low  as  1°  and  there  is  a 
complicating"  cyclophoria,  surgery  is  the  thing1  indi- 
cated. 

The  sub-ducting-  muscles  stand  in  greater  need  of  rest 
prisms  than  do  the  superducting-  muscles,  for  the  reason 
g-iven  in  the  study  of  the  posing1  of  the  head,  in  that  part 
of  this  chapter  devoted  to  symptoms.  If  there  were  no 
other  reason,  it  would  be  g-ood  practice  in  many  cases, 
not  complicated  with  minus  cyclophoria,  to  apply  the 
whole  prismatic  correction  to  the  hyperphoric  eye;  and 
certainly  this  should  be  the  practice  if  there  is  a  com- 
plicating- plus  cyclophoria,  however  small  in  quantity. 
The  superior  rectus  raising-  the  eye  to  overcome  the 
effect  of  the  prism,  in  the  interest  of  binocular  single 
vision,  torts  it  in,  thus  aiding-  the  superior  oblique  to 
parallel  the  vertical  axis  of  the  eye  with  the  median 
plane  of  the  head. 

In  the  few  cases  of  hyperphoria  and  cataphoria  that 
are  complicated  by  minus  cyclophoria,  the  whole  of  the 


376  HYPERPHORIA   AND   CATAPHORIA. 

prismatic  effect  should  be  applied  to  the  cataphoric  eye. 
The  prism,  with  its  base  up  before  this  eye,  calls  into 
action  the  inferior  rectus  in  the  interest  of  fusion;  and 
thus  aid  is  given  the  inferior  oblique  in  its  efforts  to 
parallel  the  vertical  axis  of  the  eye  with  the  median 
plane  of  the  head. 

Those  cases  of  hyperphoria  and  cataphoria  that  are 
not  complicated  by  cyclophoria  will  be  given  more  com- 
fort if  the  greater  part  (two-thirds)  of  prismatic  effect 
is  applied  to  the  hyperphoric  eye,  than  would  be  given 
if  this  rule  were  reversed,  or  even  if  the  effect  were 
equally  divided  between  the  two  eyes. 

If  the  rules  given  above  are  observed,  many  cases  will 
take  even  a  full  correction  of  the  hyperphoria,  and  not 
less  than  half  the  full  correction  should  ever  be  given. 
The  purpose  may  be  attained  either  by  prisms  or  lenses 
rendered  prismatic  by  decentration. 

Double  cataphoria  that  causes  the  patient  to  hold  his 
head  too  high  should  be  given  prisms  or  prismatic  lenses, 
bases  up,  so  as  to  let  them  assume  a  more  nearly  normal 
position  of  the  head,  provided  there  is  no  complicating 
plus  cyclophoria.  The  effect  should  be  equally  divided 
between  the  two  eyes. 

Patients  suffering  from  double  hyperphoria  should  be 
given  prisms  or  prismatic  lenses,  bases  down,  except 
when  there  is  a  complicating  minus  cyclophoria.  These 


HYPERPHORIA  AXD  CATAPHoRIA.        377 

would  enable  the  patient  to  carry  his  head  comfortably 
in  a  more  nearly  erect  position. 

Hyperphoria,  single  or  double;  cataphoria,  single  or 
double;  and  hyperphoria  of  one  eye  and  cataphoria  of 
the  other,  caused  bv  malformation  of  the  orbits,  should 
always  be  given  full  prismatic  correction  of  the  error 
found  in  each  eye. 

OPERATIVE  TREATMENT. 

A  double  hyperphoria  that  cannot  be  relieved  by  prisms 
or  by  straight-forward-to-floor  exercise,  to  the  extent  of 
enabling  the  patient  to  carry  his  head  erect,  instead  of 
downcast,  should  be  subjected  to  a  partial  tenotomy  of 
both  superior  recti.  If  there  is  no  complicating  minus 
cyclophoria,  the  tenotomies  should  be  central;  but  should 
this  complication  exist — as  it  would  if  the  superior  recti 
are  wholly  at  fault — the  tenotomies  should  be  peripheral, 
including  only  the  temporal  fibers.  Should  there  be  a 
complicating  plus  cyclophoria — as  there  would  be  if  the 
inferior  obliques  were  wholly  to  blame  for  the  double 
hyperphoria — peripheral  tenotomies  of  the  superior  recti 
should  be  done,  including  only  the  nasal  fibers.  In 
either  case,  the  operative  effect  should  be  equally  divided 
between  the  two  muscles. 

A  double  cataphoria  does  not  so  urgently  demand 
operations,  for  high-headedness  is  not  so  objectionable  as 


378         HYPERPHORIA  AND  CATAPHORIA. 

the  downcast  look.  The  position  of  the  head  in  double 
cataphoria  is  more  favorable  to  the  respiratory  act  than 
is  the  position  caused  by  double  hyperphoria — another 
reason  why  operative  interference  is  less  urgent  in  double 
cataphoria.  The  lid  pressure — pressure  of  the  upper 
lids  against  the  globe — is  much  less  in  double  cataphoria 
than  in  double  hyperphoria.  Since  great  lid  pressure  is 
probably  more  favorable  to  the  retention  and  develop- 
ment of  germs,  especially  the  trachoma  germ,  as  sug- 
gested by  Stevens,  there  is  an  additional  reason  for 
operating  more  frequently  for  double  hyperphoria  than 
for  double  cataphoria. 

Straight-forward-to-ceiling  exercise,  or  prisms  with 
their  bases  up,  should  always  be  tried  in  cases  of  double 
cataphoria;  but  should  these  fail  to  enable  the  patient  to 
carry  his  head  in  the  natural,  erect  position,  a  partial 
tenotomy  of  both  inferior  recti  should  be  done,  and  these 
operations  should  be  central,  unless  there  is  a  complicat- 
ing cyclophoria.  In  cases  in  which  there  is  a  complicat- 
ing plus  cyclophoria — as  there  would  be  if  the  double 
cataphoria  is  caused  by  the  inferior  recti — peripheral 
tenotomies  should  be  done,  including  only  the  temporal 
fibers.  In  those  cases  complicated  by  a  minus  cyclopho- 
ria, the  superior  obliques  are  the  cause;  but  since  these 
muscles  cannot  be,  or  ought  not  to  be,  operated  upon, 
peripheral  tenotomies  of  the  inferior  recti,  including  only 


HYPERPHORIA  AND  CATAPHORIA.        379 

the  nasal  fibers,  should  be  done.  The  operative  effect 
should  be  equally  divided  between  the  two  inferior  recti. 
Great  care  should  be  exercised,  in  operating-  for  double 
cataphoria,  not  to  convert  it  into  a  double  hyperphoria. 
Operations  on  the  inferior  recti  are  as  easily  done  as  on 
the  superior  recti. 

Since  double  cataphoria  is  preferable  to  double  hyper- 
phoria, there  is  g-ood  reason  for  always  operating-  first  on 
the  superior  rectus  of  the  hyperphoric  eye  in  cases  in 
which  there  is  hyperphoria  of  one  eye  and  cataphoria  of 
the  other.  While  the  tenotomy  should  never  be  com- 
plete, it  should  be  more  extensive  when  done  with  the 
view  of  lowering-  the  hyperphoric  e}re  than  when  done 
for  elevating  the  cataphoric  eye;  hence,  th<,  reason  for 
doing-  the  first  operation  as  set  forth  in  the  beg-inning-  of 
this  paragraph.  After  the  first  operation,  the  remaining- 
imbalance  must  be  corrected  by  a  partial  tenotomy  of 
the  inferior  rectus  of  the  cataphoric  eye.  As  in  the 
lateral  heterophorias,  so  in  the  vertical  errors,  tenotomies 
are  indicated  only  in  the  sthenic  forms.  A  superduction 
of  3°  or  less  should  never  be  diminished  by  lessening-  the 
tension  of  a  superior  rectus;  and  a  sub-duction  of  3°  or 
less  likewise  contraindicates  a  tenotomy.  An  asthenic 
hyperphoria  and  cataphoria  demands,  first  of  all,  a  short- 
ening- of  the  inferior  rectus  of  the  hyperphoric  eye,  by 
means  of  which  the  greater  part  of  the  effect  should  be 


380  HYPERPHORIA   AND    CATAPHORIA. 

accomplished,  the  remaining1  part  of  the  imbalance  to  be 
corrected  later  by  a  shortening1  of  the  superior  rectus  of 
the  cataphoric  eye. 

In  all  cases  of  hyperphoria  and  cataphoria,  uncompli- 
cated by  cyclophoria,  the  operations,  if  partial  tenoto- 
mies,  should  be  central;  and  if  shortenings,  should  be 
straight-forward,  so  as  not  to  change  the  plane  of  rota- 
tion. The  complication  of  plus  cyclophoria  calls  for  a 
peripheral  tenotomy  of  the  superior  rectus  of  the  hyper- 
phoric  eye,  including*  only  the  nasal  fibers,  and  a  periph- 
eral tenotomy  of  the  inferior  rectus  of  the  cataphoric 
eye,  including  only  the  temporal  fibers.  These  two 
operations  should  be  as  nearly  coextensive  as  possible, 
because  of  the  desire  to  correct  the  cyclophoria.  Should 
a  case  of  this  character  be  asthenic,  the  inferior  rectus 
of  the  hyperphoric  eye  should  be  shortened  in  such  a  way 
as  to  carry  its  plane  of  rotation  farther  in,  and  the  supe- 
rior rectus  of  the  cataphoric  eye  should  be  so  shortened 
as  to  carry  its  plane  of  rotation  farther  toward  the  tem- 
ple. The  operative  effect  should  be  equally  divided  be- 
tween the  two  muscles. 

The  complication  of  minus  cyclophoria,  which  is  rare, 
indicates  a  peripheral  tenotomy  of  the  superior  rectus  of 
the  hyperphoric  eye,  including  only  its  temporal  fibers, 
so  as  to  carry  its  plane  of  rotation  farther  toward  the 
nose,  and  a  like  operation  on  the  nasal  fibers  of  the  in- 


HYPERPHORIA   AND   CATAPHORIA.  381 

ferior  rectus  of  the  cataphoric  eye,  so  as  to  carry  its 
plane  of  rotation  farther  toward  the  temple.  An  equal 
effect  should  be  attained  by  these  two  operations.  If  a 
case  of  this  character  should  be  asthenic,  the  inferior 
rectus  of  the  hyperphoric  eye  shonld  be  so  shortened  as 
to  carry  its  plane  of  rotation  farther  toward  the  temple, 
while  the  superior  rectus  of  the  cataphoric  eye  should  be 
so  shortened  as  to  carry  its  plane  of  rotation  farther 
toward  the  nose. 

The  methods  of  doing-  these  operations  are  set  forth  in 
the  chapter  on  heterophoria,  and  the  after-treatment  is 
also  described  in  that  chapter. 


CHAPTER  VII. 


CYCLOPHORIA. 


CYCLOPHORIA  is  the  tendency  of  the  vertical  axes  of 
the  eyes  to  lose  parallelism  with  the  median  plane  of  the 
head.  In  the  interest  of  binocular  single  vision  this 
parallelism  must  be  maintained  by  the  oblique  muscles, 
except  in  cases  of  oblique  astigmatism.  For  this  pur- 
pose there  are  four  conjugate  innervation  brain-centers: 
(1)  The  sixth  conjugate  center  sends  an  impulse  to  the 
two  superior  obliques  to  prevent  divergence  of  the  verti- 
cal axes  when  the  point  of  view  is  in  the  extended  median 
plane  of  the  head,  but  below  the  extended  horizontal 
plane;  (2)  the  seventh  conjugate  center  sends  an  impulse 
to  the  two  inferior  obliques  to  prevent  convergence  of 
the  vertical  axes  when  there  is  to  be  cardinal  fixation 
above  the  horizontal  plane;  (3)  the  eighth  conjugate  cen- 
ter sends  an  impulse  to  the  superior  oblique  of  the  right 
e}Te  and  inferior  oblique  of  the  left  eye  to  prevent  torsion 
when  the  point  of  fixation  is  obliquely  up  and  to  the 
right,  or  down  and  to  the  left;  and  (4)  the  ninth  conju- 
gate center  sends  an  impulse  to  the  superior  oblique  of 
the  left  eye  and  inferior  oblique  of  the  right  eye  to  pre- 

(382) 


CYCLOPHORIA.  383 

vent  torsion  when  the  point  of  fixation  is  up  and  to  the 
left,  or  down  and  to  the  right.  Under  the  influence  of 
one  or  another  of  these  conjugate  centers,  parallelism  of 
the  vertical  axes  of  the  eyes  with  the  median  plane  of  the 
head  is  maintained,  regardless  of  the  direction  of  the  point 
of  fixation.  In  a  normal  condition  of  all  the  extrinsic  ocu- 
lar muscles,  the  obliques  accomplish  this  purpose  with 
ease.  Whenever  conditions  are  such  as  to  make  it  dif- 
ficult for  the  obliques  to  maintain  this  parallelism,  ex- 
cept when  under  an  excessive  nervous  tension,  there  is 
cyclophoria. 

When  this  condition  was  first  described  in  the  Archives 
of  Ophthalmology,  in  its  issue  of  January,  1891,  the  name 
given  it  was  "insufficiency  of  the  obliques,"  which  was 
not  inapt;  for  whatever  may  be  the  chief  cause  or  causes 
of  this  error,  the  obliques  are  insufficient  for  the  work  of 
easily  keeping  the  vertical  axes  of  the  eyes  parallel  with 
the  median  plane  of  the  head.  In  1893,  in  conformity 
with  the  terminology  introduced  by  Stevens,  the  term 
"cyclophoria"  was  coined  by  Price.  Plus  cyclophoria 
means  that  the  vertical  axes  of  the  eyes  have  a  tendency 
from  the  median  plane  of  the  head;  minus  cyclophoria 
is  "a  tendency  of  these  axes  toward  the  median  plane. 
For  the  same  conditions  Maddox  uses  the  terms  "plus 
torsion  "  and  "minus  torsion;  "  and  Stevens,  "  plus  decli- 
nation "  and  "  minus  declination."  Either  of  these  term? 


384  CYCLOPHORIA. 

would  be  as  good  as  those  coined  by  Price,  except  for 
the  desirableness  of  uniformity  in  terminology. 

While  cyclophoria  is  most  important  as  it  pertains  to 
the  two  eyes  in  their  efforts  to  maintain  binocular  single 
vision,  it  is,  nevertheless,  a  factor  for  disturbance  in 
monocular  vision.  In  order  that  the  law  of  direction 
may  not  be  interfered  with,  in  vision  with  one  eye,  its 
vertical  axis  must  always  be  parallel  with  the  median 
plane  of  the  head;  and,  necessarily,  its  transverse  axis 
must  always  lie  in  the  plane  of  the  primary  isogonal 
circle. 

There  are  two  kinds  of  cyclophoria — viz.,  symmetrical 
and  non-symmetrical.  Symmetrical  cyclophoria  is  either 
plus  or  minus  for  both  eyes;  non-symmetrical  cyclophoria 
is  plus  for  one  eye  and  minus  for  the  other.  Rarely 
there  may  be  a  plus  or  minus  cyclophoria  for  one  eye, 
while  the  obliques  of  the  other  perform  their  work 
easily.  Plus  cyclophoria  is  by  far  more  common  than 
minus  cyclophoria. 

CAUSES  OF  CYCLOPHORIA. — The  cause  may  be  wholly 
in  the  obliques.  The  nearer  the  attachment  of  an  oblique 
muscle  is  to  the  equator,  the  greater  is  its  torsioning 
power;  while  attachment  of  an  oblique  nearer  the  poste- 
rior pole  of  the  eye  gives  it  less  torsioning  power.  At- 
tachment of  both  inferior  obliques  nearer  the  equator 
than  that  of  the  superior  obliques,  would  give  a  plus 


CYCLOPHORIA.  385 

cyclophoria,  the  muscles  themselves  being  normal  in  de- 
velopment. When  the  superior  obliques  are  attached 
nearer  the  equator  than  are  the  inferior  obliques,  a  minus 
cyclophoria  would  result.  Granting-  that  the  attach- 
ments are  correct,  hyper-development  of  the  inferior  ob- 
liques or  subnormal  development  of  the  superior  obliques 
would  give  a  plus  cyclophoria;  while  hyper-development 
of  the  superior  obliques  or  subnormal  development  of  the 
inferior  obliques  would  cause  a  minus  cyclophoria.  This 
presupposes  that  the  innervations  are  normal. 

Hyper-development  of  the  seventh  conjugate  innerva- 
tion  center,  or  subnormal  development  of  the  sixth,  would 
cause  a  plus  cyclophoria;  while  hyper-development  of  the 
sixth  or  subnormal  development  of  the  seventh  conjugate 
center,  would  cause  a  minus  cyclophoria.  This  presup- 
poses that  the  muscles  themselves  are  normal  in  both 
structure  and  attachment.  In  either  case  the  plus  cy- 
clophoria would  be  complicated  by  a  double  hyperphoria, 
and  the  minus  cyclophoria  would  be  complicated  by  a 
double  cataphoria. 

A  too  high  attachment  of  the  interni  or  a  too  low  at- 
tachment of  the  extern!  would  cause  a  minus  cyclopho- 
ria, while  a  too  low  attachment  of  the  interni  or  a  too 
high  attachment  of  the  extern!  would  cause  a  plus  cyclo- 
phoria. When  there  is  a  normal  attachment  of  the  in- 
terni, there  can  result  from  their  action  no  cyclophoria. 


386  CYCLOPHORIA. 

The  superior  and  inferior  recti  constitute  the  only 
remaining*  source  of  symmetrical  cyclophoria.  When 
these  muscles  are  normal  in  structure  and  attachment, 
there  can  be  no  cyclophoria  resulting  from  their  ac- 
tion. A  double  hyperphoria  due  to  hyper-development 
of  the  superior  recti  or  subnormal  development  of  the 
inferior  recti,  gives  a  minus  cyclophoria;  while  hyper- 
developed  inferior  recti  or  subnormally  developed  supe- 
rior recti,  in  causing  double  cataphoria,  also  cause  plus 
cyclophoria. 

Non -symmetrical  cyclophoria  is  a  tendency  to  parallel 
deviation  of  the  vertical  axes  of  the  eyes,  being  plus  for 
one  eye  and  minus  for  the  other.  This  tendency  may  be 
to  the  right  or  to  the  left.  If  this  kind  of  tendency 
should  become  a  turning,  diplopia  would  not  result,  but 
there  would  be  interference  with  the  law  of  direction. 
Because  of  this  interference  the  weaker  obliques  (supe- 
rior of  one  eye  and  inferior  of  the  other)  are  kept  in  a 
state  of  nervous  tension,  that  they  may  keep  the  vertical 
axes  of  the  eyes  parallel  with  the  median  plane  of  the 
head.  The  corrective  impulse  comes  from  the  eighth  con- 
jugate center  when  the  tendency  of  the  vertical  axes  is 
toward  the  right,  and  from  the  ninth  center  when  the 
tendency  is  toward  the  left.  When  the  tendency  is 
toward  the  right,  rotation  of  the  eyes  obliquely  up 
and  to  the  right,  or  down  and  to  the  left,  is  more  dif- 


CYCLOPHORIA.  387 

ficult  than  rotation  up  and  to  the  left,  or  down  and  to 
the  right;  and  vice  versa,  when  the  tendency  is  toward 
the  left. 

The  obliques  may  cause  this  condition.  To  do  so  the 
superior  oblique  of  one  eye  must  be  too  strong  for  its  in- 
ferior oblique,  or  the  former  must  be  attached  nearer  the 
equator  than  the  latter;  while  the  inferior  oblique  of  the 
other  eye  is  either  stronger  than  its  superior  oblique  or 
is  attached  nearer  the  equator.  In  such  a  case  there 
would  be  not  only  parallel  cyclophoria,  but  there  would 
be  also  a  cataphoria  of  the  one  eye  and  a  hyperphoria  of 
the  other.  Parallel  cyclophoria  can  be  caused  by  the 
interni  when  one  is  attached  in  greater  part  above  the 
transverse  plane  of  its  eye,  while  the  other  is  attached  in 
greater  part  below  this  plane.  There  would  also  result 
a  hyperphoria  of  the  one  eye  and  a  cataphoria  of  the 
other.  Faulty  attachment  of  the  externi,  the  one  too 
high  and  the  other  too  low,  would  cause  parallel  cyclo- 
phoria. In  such  a  case  there  would  also  be  a  hyperpho- 
ria of  one  eye  and  a  cataphoria  of  the  other.  When  hy- 
perphoria of  one  eye  is  caused  by  a  too  strong  superior 
rectus  and  cataphoria  of  the  other  is  caused  by  a  too 
powerful  inferior  rectus,  parallel  cyclophoria  will  also 
result,  the  tendency  being-  to  the  right  when  there  is  left 
hyperphoria  and  to  the  left  when  there  is  right  hyper- 
phoria. 


388  CYCLOPHORIA. 

TESTS. 

Cyclophoria  was  first  discovered  in  1890  by  means  of 
a  Maddox  double  prism  which  was  being  used  for  deter- 
mining- an  imbalance  of  the  lateral  recti.  The  patient 
was  asked  if  the  middle  candle  was  in  a  vertical  line  with 
the  upper  and  lower  candles.  She  stated  that  the  lower 
candle  was  not  directly  under  the  upper  one,  although 
the  axis  of  the  double  prism  was  vertical,  or  so  judged 
by  the  eye  of  the  operator.  The  axis  of  the  prism  had 
to  be  tilted  5°  or  more  toward  the  temple  before  the 
patient  claimed  that  the  upper  and  lower  candles  were 
in  a  vertical  line.  This  showed  clearly  that  the  vertical 
retinal  meridian  was  inclined  toward  the  temple  and  to 
a  greater  extent  than  Helmholtz  had  taught  as  normal. 
At  once  a  line  was  drawn  across  a  card  and  held  before 
the  patient.  She  saw  two  lines  with  the  eye  before 
which  the  double  prism  was  held,  and  these  lines  were 
parallel.  The  other  eye  was  then  uncovered,  when  she 
saw  a  third  line  between  the  other  two  lines,  but  not 
parallel  with  them.  The  middle  line  was  seen  by  the  left 
eye,  and  it  was  seen  inclined  down  to  the  right.  Other 
cases  were  investigated,  about  twenty-five  per  cent  of 
them  showing  the  same  error  found  in  the  first  patient, 
which  was  plus  cyclophoria.  The  first  publication  was 
made  in  the  Archives  of  Ophthalmology,  Vol.  XX.,  No.  1, 
page  105.  This  paper  was  gloomy  in  that  it  presented  no 


CYCLOPHORIA.  389 

prospect  of  either  prevention  or  cure.  From  the  time  of 
the  discovery  of  cyclophoria,  in  1890,  up  to  May,  1892,  many 
cases  had  been  found,  but  none  of  them  had  been  treated; 
nor  was  it  thought  possible,  up  to  this  time,  that  any 
curative  measure  would  ever  be  devised.  On  May  17, 
1892,  the  thought  of  developing  weak  oblique  muscles  by 
exercising  them  with  cylinders  first  presented  itself. 
This  thought  was  put  into  practice  at  once,  and  the  re- 
sults were  gratifying.  This  led  to  the  presentation  of 
a  second  paper  which  was  read  before  the  Section  of 
Ophthalmology  of  the  American  Medical  Association  at 
the  Detroit  meeting,  in  June,  1892. 

The  double  prism  will  always  show  cyclophoria  when 
the  test-  object  is  a  horizontal  line.  The  kind  of  cyclo- 
phoria— whether  plus  or  minus — is  easily  ascertained  in 
this  way,  but  its  quantity  cannot  be  measured.  Substi- 
tuting a  dot  for  the  line,  the  error  may  be  measured  by 
revolving  the  double  prism  until  the  two  dots  seen 
through  the  prism  are  in  a  vertical  line.  The  extent  of 
inclination  of  the  axis  of  the  prism  would  be  equal  to  the 
amount  of  the  cyclophoria.  In  using  the  double  prism 
for  this  measurement  test  of  cyclophoria,  the  operator 
must  be  careful  to  have  the  axis  of  the  prism  vertical  in 
the  beginning  and  note  its  inclination  at  the  end  of  the 
test.  He  need  not  be  so  careful  to  have  the  patient's 
head  erect,  for  the  result  will  be  the  same  whether  the 


390  CYCLOPHORIA. 

head  is  erect  or  inclined.  However,  since  tests  of  some 
of  the  eye  muscles  require  that  the  head  shall  be  erect, 
it  is  better  to  have  it  thus  in  all  tests. 

The  cut  used  to  illustrate  the  first  paper  is  reproduced 
here,  together  with  the  descriptive  text: 

"  Place  a  double  prism,  axis  vertical,  before  one  eye,  the 
other  for  the  moment  being-  covered,  and  ask  the  patient 
to  look  at  a  horizontal  line  on  a  card  held  sixteen  inches 
away.  The  effect  of  the  double  prism  (each  6°)  is  to 
make  the  line  appear  to  be  two,  each  parallel  with  the 
other.  The  other  eye  is  now  uncovered,  and  a  third  line 
is  seen  between  the  other  two,  with  which  it  should  be 
perfectly  parallel. 

"While  a  change  of  the  position  of  the  axis,  of  the 
double  prism,  from  the  vertical  toward  the  horizontal, 
will  alter  the  distance  between  the  lines,  their  direction 
will  be  unchanged — hence,  no  loss  of  parallelism.  This 
fact  admits  of  a  little  carelessness  in  the  placing  of  the 
prism  in  the  trial  frames,  though  the  axis  should  be 
vertical,  so  as  to  give  the  maximum  distance  between 
the  two  extreme  lines. 

"If  there  is  a  want  of  harmony  on  the  part  of  the 
oblique  muscles,  this  test  will  show  it  at  once  in  a  want 
of  parallelism  of  the  middle  line  with  the  two  other 
lines,  the  right  end  of  the  middle  line  pointing  toward 
the  bottom  line  and  the  left  end  toward  the  top  line,  or 


CYCLOPHORIA. 


391 


vice  versa,  depending-  on  the   nature  of  the   individual 
case. 

"  Consider  the  eye  before  which  no  prism  is  held  as 
the  one  under  test.  With  the  double  prism  before  the 
right  eye,  the  patient  is  asked  about  the  position  and 


Fig.  48. 


Fig-  49- 


Fig.  50. 


Fig- 


Fig-  52. 

the  direction  of  the  middle  line.  It  may  be  nearer  the 
bottom  line,  thus  showing  left  hyperphoria;  or,  again, 
it  may  extend  farther  to  the  right  than  the  other  two, 
and  not  so  far  to  the  left,  thus  showing  exophoria;  or 
vice  versa,  showing  esophoria. 


392  CYCLOPHORIA. 

"If  the  right  ends  of  the  middle  and  bottom  lines  con- 
verge while  the  left  ends  diverge,  the  superior  oblique 
of  the  left  eye  is  at  once  shown  to  be  in  a  state  of  under- 
action. Fig.  48  represents  such  a  test  of  the  left  eye; 
Fig.  49  shows  a  test  of  the  left  eye  when  the  inferior 
oblique  is  the  too  weak  muscle;  Fig.  50  represents  a 
test  of  the  right  eye,  the  loss  of  the  parallelism  between 
the  lines  being  due  to  under-action  of  its  superior  oblique; 
Fig.  51,  the  same  condition  of  the  inferior  oblique 
of  the  right  eye;  Fig.  52  represents  a  test  of  both 
eyes  when  there  is  perfect  equilibrium  of  the  oblique 
muscles." 

The  single  prism  of  6°,  with  its  base  up  or  down  be- 
fore one  eye,  the  test  object  being  a  horizontal  line  on  a 
blackboard  at  twenty  feet  distance,  or  on  a  card  at  the 
reading  distance,  wrill  double  the  line.  If  the  two  are 
not  parallel,  there  is  cyclophoria.  The  false  line  inclined 
toward  the  opposite  side  shows  plus  cyclophoria;  the  same 
line  inclined  toward  the  corresponding  side  shows  minus 
cyclophoria.  The  quantity  of  the  cyclophoria  cannot  be 
measured  with  the  single  prism  by  substituting  a  dot  for 
the  line,  as  in  the  use  of  the  double  prism. 

The  rotary  prism  of  either  the  Wilson  or  the  monocu- 
lar phorometer  can  easily  show  the  existence  of  cyclo- 
phoria, or  its  absence.  As  with  other  prisms,  the  test 
object  is  a  line.  The  rotary  prism  is  adjusted  for  taking 


CYCLOPHORIA.  393 

sub-duction  and  superduction.  When  it  is  rotated  up  or 
down  beyond  the  point  of  possible  fusion,  the  line  be- 
comes double.  If  they  converge  at  one  end  or  the  other, 
there  is  cyclophoria— plus  if  the  false  line  is  inclined  to- 
ward the  opposite  side,  minus  if  it  is  inclined  toward  the 
same  side.  Rotating  the  prism  slowly  so  as  to  carry  the 
index  toward  zero,  the  two  lines  fuse,  first  at  one  end  and 
then  quickly  fuse  throughout.  The  rotary  prism  cannot 
possibly  measure  the  amount  of  cyclophoria. 

The  Stevens  clinoscope  both  detects  and  measures  any 
form  of  cyclophoria.  The  opaque  discs  with  a  single  pin, 
with  the  head  in  the  center,  drawn  on  each,  should  be 
placed  so  that  the  point  may  be  up  for  one  eye  and  down 
for  the  other.  E}ach  pin  should  be  vertical,  and  the  in- 
strument should  be  so  adjusted  as  to  allow  easy  fusion 
of  the  heads  of  the  pins.  When  the  two  discs  appear 
as  one,  the  two  pins  should  be  the  vertical  diameter  of 
the  fused  disc.  If  the  one  pin  is  a  radius  pointing  ob- 
liquely in  one  direction  and  the  other  is  a  radius  pointing 
obliquely  in  the  other  direction  (one  toward  the  right 
and  the  other  toward  the  left,  making  an  oblique  diam- 
eter), there  is  plus  cyclophoria  of  one  eye  and  minus  cy- 
clophoria of  the  other.  If  the  upper  pin  is  seen  by  the 
left  eye  and  the  lower  pin  is  seen  by  the  right  eye,  the 
two  pins  pointing  to  the  right  would  show  plus  cyclo- 
phoria; while  minus  cyclophoria  would  be  shown  by  the 


394  CYCLOPHORIA. 

two  pins  pointing1  to  the  left.  If  the  top  pin  is  vertical 
and  the  bottom  one  points  to  the  right,  there  is  plus  cy- 
clophoria  of  the  right  eye  alone;  or,  if  the  bottom  pin 
points  to  the  left,  while  the  top  one  is  vertical,  there  is 
minus  cyclophoria  of  the  right  eye  alone.  When  both 
pins  are  oblique,  the  tubes  to  which  the  discs  are  fastened 
should  be  revolved  until  the  two  pins  are  vertical,  forming 
apparently  the  vertical  diameter  of  the  fused  disc.  The 
index  connected  with  each  tube  will  point  to  the  mark  on 
the  scale  indicating  the  quantity  of  the  error  for  each  eye. 
The  errors  of  the  obliques  could  be  detected  with  equal 
ease  and  measured  with  as  much  exactness,  if  the  discs 
were  placed  so  that  the  pins  would  be  horizontal,  the  one 
seen  by  the  left  eye  pointing  to  the  left  and  the  one  seen 
by  the  right  eye  pointing  to  the  right,  their  heads  being 
fused.  To  eyes  whose  oblique  muscles  are  perfectly 
balanced  the  pins  would  appear  as  the  horizontal  diame- 
ter of  the  fused  disc.  If  the  two  pins  appear  to  point 
downward,  there  is  minus  cyclophoria;  if  they  appear 
to  point  upward,  there  is  plus  cyclophoria.  If  the  left 
pin  points  downward,  while  the  right  pin  points  upward, 
there  is  minus  cyclophoria  of  the  left  eye  and  plus  cyclo- 
phoria of  the  right  eye  (parallel  cyclophoria).  In  either 
case,  rotation  of  the  two  tubes  until  the  pins  appear  to 
be  horizontal,  constituting  the  apparent  horizontal  diam- 
eter of  the  fused  disc,  measures  the  error. 


CYCLOPHORIA.  395 

The  cyclo-phorometer  will  also  detect  and  measure  both 
symmetrical  and  non-symmetrical  cyclophoria.  The  in- 
strument must  be  perfectly  level,  and  the  index  of  each 
triple  rod  must  stand  at  zero.  The  5°  prism,  base  up, 
must  be  placed  in  the  slot  behind  one  rod,  while  a  red 
glass  may  be  put  in  the  slot  behind  the  other  rod.  The 
test  object  must  be  a  candle,  gas  jet,  or  small  electric 
light.  The  red  streak  above  and  the  yellow  streak  be- 
low must  be  made  even  by  the  regulating  screw.  To 
perfectly  balanced  eyes  these  streaks  would  appear  par- 
allel. If  the  red  streak  is  seen  by  the  right  e}Te  and 
the  two  converge  at  the  left,  there  is  plus  cyclophoria; 
if  they  converge  at  the  right,  there  is  minus  cyclophoria. 
If  they  appear  parallel,  but  inclined,  there  is  plus  cyclo- 
phoria of  one  eye  and  minus  cyclophoria  of  the  other. 
If  one  is  horizontal  and  the  other  is  inclined,  there  is  cy- 
clophoria of  one  eye  alone.  The  disc  containing  the  rods 
should  be  turned  until  both  streaks  are  perfectly  hori- 
zontal and,  therefore,  parallel.  If  the  index  of  each  stands 
in  the  nasal  arc  when  the  streaks  are  made  to  appear 
horizontal,  there  is  plus  cyclophoria;  and  if  they  stand  in 
the  temporal  arcs,  there  is  minus  cyclophoria.  The 
quantity  of  the  error  in  each  eye  is  measured  by  the  arc 
traversed  by  the  index  and  is  shown  on  the  scale.  If 
only  one  rod  is  turned  until  the  two  streaks  become  par- 
allel, but  not  horizontal,  the  quantity  marked  by  the  in- 


396  CYCLOPHORIA. 

dex  is  the  sum  of  the  cyclophoria  of  the  two  eyes.  If 
there  is  parallel  cyclophoria,  the  quantity  is  shown  by 
revolving-  the  two  rods  until  the  two  streaks  are  hori- 
zontal. 

Cyclo-duction  can  be  taken  either  with  the  clinoscope 
or  the  cyclo-phorometer.  If  the  clinoscope  is  used,  the 
discs,  with  a  diameter  drawn  across  each,  should  be  at- 
tached. They  can  be  set  with  the  diameters  either  ver- 
tical or  horizontal.  When  vertical,  revolving  the  tubes 
so  that  the  lines  shall  deviate  from  each  other  above 
will  put  into  action  the  inferior  obliques.  If  only  one  tube 
is  revolved,  only  one  inferior  oblique  is  called  into  action, 
while  revolving  both  tubes  will  call  into  action  both  in- 
ferior obliques.  The  normal  duction  power  of  the  ob- 
liques is  not  so  well  known  as  that  of  the  recti.  It  is 
somewhere  between  7°  and  14°  for  one,  and  22°  or  less,  for 
both  inferior  obliques. 

Revolving  the  tubes  so  that  the  lines  converge  above 
puts  the  superior  obliques  to  the  strength  test.  If  only 
one  tube  is  revolved,  only  one  superior  oblique  is  called 
on  for  a  fusion  effort;  but  if  both  are  revolved,  both  eyes 
must  be  cyclo-ducted  by  the  two  superior  obliques.  The 
fusion  power  of  the  superior  obliques  is  less  than  that  of 
the  inferior  obliques,  but  how  much  less  normally  is  not 
known.  In  plus  cyclophoria,  minus  cyclo-duction  is  di- 
minished and  plus  cyclo-duction  is  increased;  while  in 


CYCLOPHORIA.  397 

minus  cyclophoria,  plus  cyclo-duction  is  less  and  minus 
cyclo-duction  is  greater.  In  taking-  either  minus  or  plus 
cyclo-duction  the  revolution  of  the  cylinders  must  be 
stopped  the  moment  the  lines  begin  to  be  seen  separate- 
ly. The  index  will  point  to  the  number  indicating  the 
extent  of  the  fusion  rotation. 

Placing  the  discs  so  that  the  two  diameters  shall  be 
horizontal,  both  plus  and  minus  cyclo-duction  can  be 
taken  as  easily  and  accurately  as,  if  not  more  accurate- 
ly than,  when  these  lines  are  vertical.  Rotating  the  tubes 
so  that  these  lines  are  made  to  point  downward  at  their 
outer  ends  will  call  into  fusion  activity  the  two  inferior 
obliques,  while  rotating  them  so  that  they  shall  point 
upward  will  excite  into  fusion  activity  the  superior  ob- 
liques. 

When  the  cyclo-phorometer  is  used  for  measuring  the 
fusion  power  of  the  obliques,  the  instrument  should  be 
adjusted  as  for  testing  for  cyclophoria.  As  soon  as  the 
rods  are  so  rotated  that  the  one  streak  of  light  is  di- 
rectly under  the  other,  both  the  displacing  prism  and 
the  red  glass  should  be  removed.  At  once  the  two  lines 
would  be  fused  into  one  horizontal  line.  Revolving  one 
rod  so  that  the  index  shall  move  in  the  nasal  arc  puts  to 
the  test  the  inferior  oblique  of  that  eye;  revolving  both 
rods  so  that  each  index  shall  be  in  the  nasal  arc  puts 
both  inferior  obliques  to  the  test.  When  the  two  streaks 


398  CYCLOPHORIA. 

of  light  are  well  defined  and  exactly  alike  as  to  width 
and  color,  the  plus  cyclo-duction  should  be  as  great  with 
this  instrument  as  with  the  clinoscope. 

Revolving-  the  rods  so  that  the  index  of  each  shall 
move  in  the  temporal  arc,  excites  into  fusion  activit}-  both 
superior  obliques.  If  one  alone  is  to  be  tested,  only  the 
one  rod  should  be  revolved,  the  other  being-  allowed  to 
stand  at  zero.  Thus  plus  and  minus  cyclo-duction  should 
be  taken  in  all  cases  of  cyclophoria;  and  even  when  there 
is  no  cyclophoria,  these  should  be  taken  and  noted,  so 
that  a  standard  may  be  attained. 

The  first  instrument  for  taking-  cyclo-duction  was  in- 
vented by  Dr.  C.  H.  Perry,  of  Oneida,  N.  Y.,  and  for 
this  purpose  is  but  little,  if  at  all,  inferior  to  the  clino- 
scope or  the  cyclo-phorometer.  A  description  of  this  in- 
strument and  its  use  was  published  by  the  Ophthalmic 
Record,  in  its  issue  of  November,  1895,  in  the  inventor's 
own  lang-uag-e.  It  reads  as  follows: 

"Fig1.  53  represents  a  stereoscopic  card,  to  which  are 
centrally  pivoted  two  thin  discs,  each  three  inches  in 
diameter,  their  centers  being-  three  inches  apart  in  a  hor- 
izontal line. 

"These  discs  are  mashed  tog-ether  at  their  point  of 
contact  by  a  single  interlocking  slot  in  each. 

"  The  left  disc  is  moved  by  a  lever  passing  under  the 
right,  and  is  provided  with  an  index,  which  shows,  on  a 


CYCLOPHORIA. 


399 


graduated  scale  at  the  right-hand  of  the  card,  the  num- 
ber of  degrees  that  each  disc  is  rotated.  Having  equal 
diameters,  and  being  geared  together,  the}-  move  syn- 
chronously equal  distances,  but  in  opposite  directions. 


.  53- 


Horizontally  over  the  center  of  each  disc  is  printed  a 
word,  and  vertically  through  each  of  said  centers  is 
drawn  a  line. 

"When  this  apparatus  is  seen  in  a  stereoscope  and  the 
discs  are  rotated  by  moving  the  lever,  the  two  words 
will  remain  blended  while  each  disc  moves  through  an 
arc  of  about  5°  (and  much  more  in  some  subjects);  and  if 
attention  is  given  to  the  perpendicular  lines,  they  will 
appear  as  a  single  line  during  the  rotation  of  about  the 
same  arc.  If  used  with  due  care,  this  instrument  gives 
a  practically  accurate  measurement  not  only  of  the  rela- 


400  CYCLOPHORIA. 

tive,  but  of  the  absolute,  power  of  rotation  in  each  direc- 
tion." 

Cyclo-version  is  impossible,  since  voluntary  rotation  of 
the  eyes  around  the  visual  axes  cannot  be  accomplished. 

In  the  study  of  the  causes  of  cyclophoria,  all  of  the 
complications  have  been  considered.  Under  the  head 
"Treatment"  they  will  be  referred  to  ag-ain,  since  the 
treatment,  whether  surg-ical  or  otherwise,  is  largely  de- 
termined by  these  complications. 

SYMPTOMS. 

Any  one  or  several  of  the  symptoms  mentioned  in  the 
chapter  on  heterophoria  may  result  from  cyclophoria. 
Vertigo  and  nausea  are  more  commonly  found  associated 
with  cyclophoria  than  with  any  other  form  of  heteropho- 
ria. As  already  shown  in  the  study  of  hyperphoria  and 
cataphoria,  it  is  plus  cyclophoria  that  causes  the  tilting- 
of  the  head  toward  the  cataphoric  side,  and  minus  cyclo- 
phoria that  causes  the  tilting"  of  the  head  toward  the 
hyperphoric  side. 

Symmetrical  plus  cyclophoria  associated  with  double 
hyperphoria  causes  hig'h-headedness,  for  the  reason  that 
the  superior  obliques  can  more  easily  counteract  a  plus 
cyclophoria  when  the  visual  axes  are  depressed  below 
the  extended  horizontal  plane  of  the  head.  Symmetrical 
minus  cyclophoria  with  double  cataphoria  causes  the  pa- 


CYCLOPHORIA.  401 

tient  to  carry  his  head  thrown  forward,  giving-  a  down- 
cast appearance,  because,  in  this  position,  the  inferior 
oblique  can  counteract  more  easily  the  minus  cyclophoria. 

TREATMENT. 

Rest  cylinders,  exercise  cylinders,  and  operations  on 
the  recti  constitute  the  means  for  curing-  cyclophoria. 
When  cyclophoria  was  discovered,  in  1890,  a  cure  was 
thought  to  be  impossible.  In  1892  the  first  case  was 
treated  with  exercise  cylinders.  In  1888  the  late  Dr. 
H.  Culbertson,  in  a  paper  read  by  him  before  the  Section 
of  Ophthalmology  of  the  American  Medical  Association, 
embodied  the  idea  of  the  usefulness  of  cylinders  not  only 
for  the  correction  of  astigmatism,  but  also  for  giving  rest 
to  weak  oblique  muscles.  The  title  of  that  paper  was 
"Binocular  Astigmatism,"  and  in  it  he  advocated  rotat- 
ing cylinders  out  of  the  positions  indicated  in  the  monoc- 
ular test,  so  that  distortions  of  objects  might  be  over- 
come. He  claimed,  and  correctly  so,  that  many  of  his 
patients  obtained  comfort  from  this  procedure.  He 
claimed  no  basis  for  this  practice  other  than  empiri- 
cism, whereas  there  is  a  scientific  basis  for  it,  which 
will  be  given  farther  on. 

The  germ  of  the  idea  of  operating  on  the  recti  so  as  to 
help  weak  obliques  is  embodied  in  language  found  in  the 
Ophthalmic  Record,  in  its  issue  of  March,  1893.  These 


402  CYCLOPHORIA. 

are  the  words:  "/«  doing- advancement  operations  on  the 
recti  muscles,  one  of  the  chief  dangers  is  turning'  the  eye- 
ball on  its  antero-posterior  diameter  so  as  to  throw  un- 
bearable strain  on  either  the  superior  or  inferior  oblique 
muscles."  At  once  it  should  have  occurred  to  the  author 
of  the  quotation  just  made  that,  naturally,  the  recti  might 
be  so  attached  as  to  do  the  very  same  thing1 — that  is,  de- 
velop a  cyclophoria. 

While  in  attendance  on  the  first  Pan-American  Medi- 
cal Congress,  Dr.  Swan  M.  Burnett  suggested  to  the 
author  that  the  superior  and  inferior  recti  might  have 
such  a  scleral  attachment  as  to  throw  an  undue  amount 
of  strain  on  the  obliques.  On  hearing-  this  statement 
the  author  made  this  suggestion:  " If  you  are  correct, 
some  cases  of  insufficiency  of  the  obliques  can  be  cured 
by  dividing  the  offending- fibers  of  the  inferior  (or  supe- 
rior} recti."  This  was  published  in  the  first  edition 
of  "New  Truths  in  Ophthalmology"  (1893),  page  41. 

REST  CYLINDERS. — These  can  be  given  for  either  plus 
or  minus  cyclophoria  even  when  there  is  no  astigmatism 
to  be  corrected.  The  objection  to  this  practice  is  that, 
while  they  give  rest  to  the  weak  obliques,  they,  at  the 
same  time,  make  images  on  the  retinas  less  distinct.  It 
is  the  distorting,  or  it  would  probably  be  better  to  say 
"  the  displacing, "  of  images  that  gives  rest  to  the  weaker 
obliques.  It  is  no  longer  denied  that,  in  astigmatism, 


CYCLOPHORIA.  403 

all  lines  not  parallel  with  one  or  the  other  of  the  two 
principal  meridians  have  their  images  displaced  toward 
the  meridian  of  greatest  curvature.  To  fuse  such  dis- 
placed images  (displaced  in  opposite  directions)  there 
must  be  cyclotropia,  just  as  there  must  be  esotropia  in 
order  to  fuse  images  that  are  thrown  to  the  temporal 
side  of  the  maculas  by  prisms  with  their  bases  out. 
The  law  of  corresponding  retinal  points,  which  is  su- 
preme, compels  the  cyclotropia  of  oblique  astigmatism, 
notwithstanding  it  must  interfere  with  the  law  of  direc- 
tion, in  that  the  vertical  axes  of  the  eyes  are  made  either 
to  converge  or  diverge  above.  Artificial  oblique  astig- 
matism produces  the  same  changes  in  images  of  vertical 
and  horizontal  lines  as  does  natural  oblique  astigmatism. 
When  there  is  plus  cyclophoria,  natural  oblique  astig- 
matism of  1  or  2  D,  with  the  meridians  of  greatest 
curvature  converging  above,  is  often  attended  by  more 
comfort,  because  of  the  rest  it  gives  to  the  superior  ob- 
liques, than  the  correcting  cylinders  would  give;  for 
when  the  correction  is  given,  the  image  of  every  line  in 
space  is  in  a  plane  with  the  line  itself,  and  to  fuse  these 
images  the  weak  superior  obliques  must  parallel  the 
vertical  axes  of  the  eyes  with  the  median  plane  of  the 
head.  To  do  this  their  normal  tension  must  be  sup- 
plemented by  a  nervous  tension  which  they  poorly  bear. 
What  natural  astigmatism  will  do,  artificial  astigmatism 


404  CYCLOPHORIA. 

will  accomplish.  Only  weak  cylinders  should  be  used 
for  non-astigmatics,  with  the  view  of  resting-  weak 
oblique  muscles.  More  than  1  D,  whether  the  axis  be 
made  to  incline  little  or  much,  would  blur  objects  un- 
necessarily. Cylinders  of  .50  D  are  usually  strong- 
enough,  especially  when  their  axes  are  made  to  incline 
far  toward  maximum  points,  in  the  proper  arcs.  For 
plus  cyclophoria  the  arc  of  distortion  for  plus  cylinders 
is  the  lower  nasal  arc;  for  minus  cylinders,  the  lower 
temporal  arc.  The  maximum  distortion  by  the  cylin- 
der is  accomplished  when  its  axis  stands  at  45°  from 
the  vertical.  For  minus  cyclophoria  the  arc  of  distor- 
tion for  plus  cylinders  is  the  lower  temporal  arc;  for 
minus  cylinders,  the  lower  nasal  arc.  For  non-astig- 
matics each  arc  of  distortion  is  90°,  the  distortion  or  dis- 
placement gradually  increasing  as  the  axis  of  the  cylin- 
der is  carried  up  to  the  midway  point  (45°)  of  the  arc,  and 
then  gradually  grows  less  as  the  axis  is  carried  on  toward 
the  horizontal,  at  which  point  there  can  be  no  distortion. 
The  most  useful  cylinder  is  a  plus  .50  D  when  there  is 
esophoria  as  well  as  cyclophoria,  or  a  minus  .50  D  when 
there  are  exophoria  and  cyclophoria.  The  quantity  of  the 
cyclophoria  determines  the  location  of  the  axes  of  the  cylin- 
ders, but  in  no  case  need  they  be  placed  farther  from  the 
vertical  than  45°,  for  this  is  the  point  where  they  accom- 
plish the  maximum  distortion,  thereby  securing,  for  the 


CYCLOPHORIA.  405 

weak  obliques,  the  greatest  amount  of  rest.  Given  a 
case  of  plus  cyclophoria  that  is  also  esophoric,  but  non- 
astigmatic,  to  obtain  rest  for  the  weak  superior  obliques 
a  plus  .50  D  cylinder  should  be  given  for  each  eye,  placing 
the  axis  of  the  right  cylinder  at  some  point  between  90° 
and  135°  or  at  the  latter,  while  placing  the  axis  of  the 
left  cylinder  at  some  point  between  90°  and  45°  or  at  the 
latter.  These  cylinders  will  give  additional  comfort  to 
nearly  all  cases  of  this  kind. 

It  is  better,  however,  to  cure  these  cases  either  by  ex- 
ercising the  weak  superior  obliques  or  by  operating  on 
the  interni. 

If  there  is  a  hyperphoria  of  one  eye  and  a  cataphoria 
of  the  other,  as  well  as  plus  cyclophoria,  the  rest  cylinder 
should  be  applied  only  to  the  cataphoric  eye.  The  infe- 
rior oblique,  in  torting  this  eye  out  for  fusing  images  with 
the  fellow  eye,  would  also  elevate  the  eye,  counteracting 
the  cataphoria.  For  a  like  reason,  the  rest  cylinder  should 
be  applied  only  to  the  hyperphoric  eye  for  the  relief  of 
minus  cyclophoria.  But  it  would  be  better  practice  to 
cure  the  plus  cyclophoria  by  a  marginal  tenotomy  (on 
nasal  side)  of  the  superior  rectus  of  the  hyperphoric  eye, 
or  by  exercising  both  superior  obliques. 

Cylinders  given  for  the  correction  of  astigmatism,  ob- 
lique or  non-oblique,  may  be  so  placed  as  to  give  rest  to 
weak  superior  obliques  when  there  is  plus  cyclophoria, 


406  CYCLOPHORIA. 

or  to  weak  inferior  obliques  when  there  is  minus  cyclo- 
phoria.  If  the  astigmatism  is  vertical  and  hyperopic, 
the  arc  of  distortion  by  the  plus  cylinder  for  the  superior 
oblique  is  90°,  and  that  for  the  inferior  oblique  is  also 
90°,  their  sum  being  180°;  if  the  astigmatism  is  oblique, 
the  meridian  of  greatest  curvature  of  the  right  eye  being 
at  60°  and  that  of  the  left  eye  at  120°,  the  arc  of  distor- 
tion by  the  correcting  cylinders  for  the  superior  obliques 
will  be  30°,  and  that  of  the  inferior  obliques  will  be  150°, 
their  sum  being  180°.  If  the  meridian  of  greatest  curva- 
ture of  the  right  eye  is  at  45°,  and  of  the  left  eye  at  135°, 
there  is  no  arc  of  distortion  for  the  superior  obliques, 
but  the  arc  of  distortion  for  the  inferior  obliques  is  180°. 
The  center  of  the  arc  of  distortion  by  plus  cylinders  for 
the  superior  obliques  is  at  45°  in  the  lower  temporal  arcs, 
and  for  the  inferior  obliques  is  at  45°  in  the  lower  nasal 
arcs.  This  is  reversed  in  the  use  of  minus  cylinders. 
This  will  be  elucidated  further  in  the  chapter  on  cy- 
clotropia. 

Prom  what  has  just  been  said,  it  will  be  understood 
that,  when  plus  cylinders  are  used  for  correcting  astig- 
matic errors,,  their  axes  must  be  turned  from  the  point 
indicated  by  the  astigmatism  toward  the  center  of  the 
lower  nasal  arc  for  the  relief  of  weak  superior  obliques 
in  plus  cyclophoria,  and  toward  the  center  of  the  lower 
temporal  arc  for  the  relief  of  weak  inferior  obliques  in 


CYCTvOPHOKIA.  407 

minus  cyclophoria.  The  extent  of  the  displacement  of 
the  axes  depends  both  on  the  strength  of  the  cylinders 
and  the  quantity  of  the  cyclophoria.  Rarely  should  this 
displacement  be  more  than  5°  if  the  cylinders  are  plus  1 
D,  or  stronger;  but  weaker  cylinders  may  be  revolved 
much  farther. 

Culbertson  displaced  the  axes  of  his  cylinders  with  the 
view  of  correcting-  the  appearance  of  slanting  floors, 
leaning  walls,  and  distorted  figures,  without  any  refer- 
ence at  all  to  the  oblique  muscles;  but,  after  all,  the 
benefit  derived  was  from  giving  rest  to  the  weak  ob- 
liques. In  vertical  astigmatism,  the  cylinders  do  not 
cause  the  floor  to  slant  or  the  wall  to  lean;  and  yet  it  is 
just  as  essential  to  displace  the  axes  of  the  correcting 
cylinders  in  the  proper  arcs,  when  there  is  cyclophoria,  as 
it  is  to  displace  the  axes  of  cylinders  correcting  oblique 
astigmatism. 

In  1894,  Nettleship,  and  probably  others  on  the  staff 
of  the  Royal  Ophthalmic  Hospital,  London,  was  in  the 
habit  of  directing  that  the  axes  of  cylinders  should  be 
placed  at  90°  or  180°,  when  accurate  measurements 
showed  that  the  two  principal  meridians  were  removed 
only  a  few  degrees  from  these  points.  When  asked  why 
he  did  this,  he  said  that  some  patients  derived  more  com- 
fort from  the  displaced  cylinders.  There  was  then  pres- 
ent a  female  patient  who  could  not  wear  her  cylinders 


408  CYCLOPHORIA. 

thus  displaced.  Inquiry  elicited  the  fact  that  she  had 
been  given  plus  cylinders — axes,  90° — for  each  eye,  when 
the  record  showed  that  the  meridian  of  greatest  curvature 
of  the  right  eye  was  at  100°,  and  of  the  left  eye  at  80°. 
These  cylinders  were  displaced  in  the  arcs  of  distortion 
for  the  superior  obliques,  which  were  evidently  too  weak 
to  bear  the  consequent  over-action.  In  that  case,  it  would 
have  been  better  to  have  displaced  these  axes  farther  from 
the  vertical  instead  of  to  it. 

Better  than  displacing  the  axes  of  correcting  cylinders, 
so  that  they  may  give  rest  to  the  weak  oblique  muscles, 
is  to  make  these  muscles  strong  by  exercise,  or  else  cor- 
rect the  cyclophoria  by  operating  on  one  or  more  of  the 

recti. 

EXERCISE  OF  THE  OBLIQUES. 

This  can  be  accomplished  by  the  Perry  cards  (see  Fig. 
53)  used  in  the  stereoscope.  This  would  require  the  time 
of  the  surgeon  or  his  assistant,  throughout  each  exercise, 
for  revolving  the  cards.  Depressing  the  handle  would 
make  the  printed  word  incline  toward  the  opposite  side; 
and  to  keep  the  two  words  fused,  the  superior  obliques 
would  be  called  into  action.  Again,  raising  the  handle, 
so  that  the  pointer  shall  stand  at  zero,  will  bring  the  two 
words  into  a  horizontal  line,  and  thus  cause  the  superior 
obliques  to  relax.  Repeating  these  steps,  alternate  con- 
traction and  relaxation  of  the  superior  obliques  can  be 


CYCLOPHORIA.  409 

accomplished.  This  exercise  stopped  short  of  fatigue 
would  tend  to  strengthen  these  muscles,  and  thus  cure 
the  plus  cyclophoria. 

In  minus  cyclophoria  the  discs  would  have  to  be  so  ro- 
tated as  to  make  the  words  incline  toward  the  corre- 
sponding- side,  in  order  to  call  into  action  the  inferior  ob- 
liques. 

The  Stevens  clinoscope  also  can  be  used  for  exercising* 
the  obliques;  but  this,  too,  would  require  the  time  of  the 
surgeon  or  his  assistant.  The  discs  used  should  be  those 
marked  with  the  diameter,  and  not  with  the  radius,  un- 
less the  two  radii  should  be  made  both  to  point  in  the 
same  direction.  The  former  would  be  better.  The 
discs  could  be  placed  with  the  diameters  either  vertical 
or  horizontal.  Revolving1  the  two  tubes,  so  that  the 
indicators  would  point  toward  each  other,  would  call 
into  action  the  superior  oblique  muscles;  but  when  made 
to  diverge  from  each  other,  the  inferior  obliques  would  be 
called  into  action.  Reversing-  the  revolution,  in  either 
case,  so  that  each  indicator  would  stand  at  zero,  would 
bring-  the  obliques  into  the  state  of  rest.  In  this  way 
rhythmic  exercise  of  the  obliques  may  be  accomplished, 
and  a  plus  or  minus  cyclophoria  cured. 

The  cyclo-phorometer  likewise  can  be  used  for  exer- 
cising- the  obliques;  but  this,  too,  would  require  the  time 
of  the  surgeon  or  his  assistant.  It  should  be  adjusted 


410  CYCLOPHORIA. 

for  easy  fusion  of  the  two  streaks  of  light,  as  if  for  the 
purpose  of  taking-  the  cyclo-duction.  Revolving1  the  two 
rods,  so  that  the  indicators  would  move  in  the  temporal 
arcs,  would  call  into  action  the  superior  obliques;  and 
revolving-  them  so  that  the  indicators  would  move  in  the 
nasal  arcs  would  call  into  action  the  inferior  obliques.  In 
either  case,  reversing-  the  motion,  so  that  the  indicators 
may  be  made  to  stand  at  zero,  would  cause  relaxation  of 
these  muscles.  The  revolutions  could  be  repeated  so  as  to 
cause  rhythmic  exercise  of  the  obliques,  and  thus  cure 
cyclophoria.  The  displacement  should  not  be  more  than 
half  that  for  cyclo-duction  in  either  of  these  methods. 

Whether  the  one  or  the  other  of  these  means  should 
be  used,  the  exercise  should  not  cause  fatigue,  and  in  no 
case  should  it  be  continued  longer  than  ten  minutes.  It 
need  not  be  repeated  oftener  than  once  a  day. 

The  only  means  for  exercising  the  oblique  muscles, 
which  a  patient  can  use  without  assistance,  consists  of  a 
pair  of  cylinders  set  in  circular  rims,  so  that  they  may 
be  turned  in  the  proper  directions  for  displacing  a  hori- 
zontal line  so  as  to  call  into  action  the  proper  muscles  in 
the  treatment  of  cyclophoria.  The  frames  for  this  pur- 
pose are  made  of  German  silver,  with  circular  rims. 
These  rims  are  deeply  grooved  to  allow  a  free  rotation 
of  the  lenses.  The  rims  are  marked  at  points  fifteen 
degrees  apart,  from  90°  to  45°,  in  either  the  lower  tern- 


CYCLOPHORIA. 


411 


poral  or  lower  nasal  quadrant,  depending-  on  the  pair  of 
muscles  affected.  The  cylinders  used  are  usually  plus 
1.50  D.,  and  the  axis  of  each  is  plainly  marked,  as  shown 
in  the  cuts.  The  frames  are  not  marked,  nor  are  the 
cylinders  cut,  except  by  the  oculist's  order. 

Fig-.  54  represents  a  pair  of  exercise  cylinders  ordered 
for  a  patient's  own  use,  whose  superior  obliques  are  in- 
sufficient. The  rims,  as  shown,  are  marked  in  the  lower 


Fig-  54- 

temporal  quadrant,  at  four  points  fifteen  degrees  apart- 
three  of  which  are  numbered  1,  2,  and  3.  The  cylinders, 
whose  axes  are  distinctly  marked,  can  be  readily  revolved- 
The  patient  is  directed  to  place  the  mark  on  each  lens  at 
the  notch  marked  No.  1.  Placing-  them  now  before  her 
eyes,  she  is  instructed  to  look  at  a  horizontal  line  eigfht  or 
ten  feet  distant  for  five  seconds,  then  without  them  for  five 
seconds,  then  ag-ain  with  them  for  five  seconds,  and  so  on 


412  CYCLOPHORIA. 

for  five  minutes.  Now  the  two  lenses  are  to  be  revolved  so 
that  their  marks  point  to  the  No.  2  notch  on  the  rim. 
The  line  is  now  looked  at,  as  above,  for  three  minutes. 
Now  the  last  change  in  position  of  the  lenses  is  made 
by  revolving-  their  marks  to  notch  No.  3,  the  point  of 
maximum  action.  The  patient  again  looks  at  the  line,  as 
above,  for  two  minutes,  which  ends  the  exercise  for  that 
day — ten  minutes  in  all. 

The  marking  of  the  rims  must  be  in  the  lower  nasal 
quadrant  when  the  patient  has  insufficiency  of  the  inferior 
obliques,  the  exercise  lenses  to  be  plus  cylinders.  The 
revolution  is  made  in  the  direction  of  the  notching-  in  both 
classes  of  cases.  The  points  at  which  to  stop  and  the 
time  to  look  at  the  line  are  the  same  for  both  plus  and 
minus  cyclophoria.  The  exercise  is  accomplished  by  rais- 
ing- and  lowering-  the  frames  at  intervals  of  three  seconds. 
This  exercise  should  not  be  carried  to  the  point  of  fa- 
tig-ue,  nor  should  it  be  continued  long-er  than  ten  minutes. 

Once  a  day  is  sufficiently  often  to  resort  to  the  exer- 
cise. The  lig-htest  work  is  done  when  the  axes  of  the 
cylinders  stand  at  the  first  notch,  and  it  is  continued 
long-est;  while  the  heaviest  work  is  demanded  when  the 
axes  stand  at  the  hig-hest  notch,  and  for  this  reason  it  is 
continued  the  shortest  time. 

It  is  clear  that  these  cylinders  are  intended  for  the 
production  of  artificial  oblique  astig-matism,  which  must 


CYCLOPHORIA.  413 

effect  the  same  changes  in  images  as  are  found  in  natural 
oblique  astigmatism.  Plus  cylinders  revolved  as  shown 
in  Fig.  54  make  the  meridians  of  greatest  refraction 
diverge  from  each  other  above;  for  the  axes  of  the  cylin- 
ders, representing  the  meridians  of  least  curvature,  con- 
verge above.  These  cylinders  make  horizontal  lines  dip 
toward  the  opposite  side.  To  keep  the  images  fused,  the 
superior  obliques  must  tort  the  eyes  in.  Raising  the 
frames,  the  images  of  the  horizontal  line  are  no  longer 
oblique,  hence  the  muscles  that  torted  the  eyes  in  must 
now  relax. 

If  minus  cylinders  are  used,  their  axes  should  be  placed 
in  the  nasal  arcs  of  the  frames  for  exercising  the  superior 
obliques,  and  in  the  temporal  arcs  for  exercising  the  in- 
ferior obliques.  The  axis  of  the  minus  cylinder  repre- 
sents the  meridian  of  most  refraction,  hence  the  need 
for  rotating  it  in  a  direction  different  from  that  for  the 
plus  cylinder. 

The  cylinders,  whether  plus  or  minus,  may  be  of  any 
strength  from  .50  D  to  1.50  D.  Rarely  should  the 
cylinder  be  stronger  than  1.50  D. 

These  cylinders  were  first  used  for  exercising  the  ob- 
liques on  May  17,  1892.  The  first  case  was  cured  of  a 
plus  cyclophoria  after  a  reasonably  short  time  of  faith- 
ful exercise,  and  remains  cured  to  this  day — September 
26,  1901. 


414  CYCLOPHORIA. 

OPERATIVE  TREATMENT. 

A  plus  cyclophoria  uncomplicated  by  any  other  form 
of  imbalance,  if  high  in  degree  and  unrelievable  by  non- 
surgical  means,  should  be  treated  by  operating  on  both 
superior  recti,  dividing  only  their  nasal  fibers;  or  by 
operating  on  both  inferior  recti,  shortening  or  advancing 
their  nasal  fibers.  In  either  case,  the  cyclophoria  would 
be  cured  and  double  cataphoria  would  be  developed. 

A  plus  cyclophoria  complicated  by  a  double  hyperpho- 
ria  should  be  relieved  by  cutting  the  nasal  fibers  of  both 
superior  recti,  which  should  result  in  a  cure  of  both  con- 
ditions. 

A  plus  cyclophoria  complicated  by  double  cataphoria 
should  be  treated  by  dividing  the  temporal  fibers  of  both 
inferior  recti. 

A  plus  cyclophoria  complicated  by  right  hyperphoria 
and  left  cataphoria  calls  for  a  division  of  the  nasal  fibers 
of  the  right  superior  rectus  and  the  temporal  fibers  of 
the  left  inferior  rectus.  These  operations  should  cure 
both  conditions. 

A  plus  cyclophoria  complicated  by  sthenic  esophoria 
should  be  treated  by  dividing  the  lower  fibers  of  both  in- 
terni;  but  when  the  esophoria  is  asthenic,  the  operation 
should  be  a  shortening  or  advancement  of  the  lower  fibers 
of  both  externi. 

A  plus  cyclophoria  complicated  by  sthenic  exophoria 


CYCLOPHORiA.  415 

calls  for  a  division  of  the  upper  fibers  of  both  externi; 
but  when  the  exophoria  is  asthenic,  the  upper  fibers  of 
both  interni  either  should  be  shortened  or  advanced. 

A  plus  cyclophoria  complicated  by  sthenic  esophoria, 
right  hyperphoria,  and  left  cataphoria,  demands  that  the 
lower  fiber,  of  the  left  internus  should  be  divided,  so  as 
both  to  elevate  the  cataphoric  eye  and  tort  it  in.  If  there 
remains  some  of  both  the  plus  cyclophoria  and  right  hy- 
perphoria, the  nasal  fibers  of  the  right  superior  rectus 
should  be  cut. 

A  plus  cyclophoria  complicated  by  sthenic  exophoria, 
right  hyperphoria,  and  left  cataphoria,  calls  for  a  division 
of  the  upper  fibers  of  the  right  externus,  so  as  both  to 
depress  the  hyperphoric  eye  and  tort  it  in.  Should  there 
remain  some  of  the  plus  cyclophoria  and  left  cataphoria, 
the  temporal  fibers  of  the  left  inferior  rectus  should  be 
severed. 

Very  rarely  there  is  minus  cyclophoria,  either  compli- 
cated or  uncomplicated,  that  calls  for  surgical  treatment. 
It  only  must  be  remembered  that  the  part  of  a  muscle 
cut,  shortened,  or  advanced  for  plus  cyclophoria  must 
remain  intact  when  the  condition  is  minus  cyclopho- 
ria; and  that  the  margins  left  intact  in  the  treatment  of 
plus  cyclophoria  must  be  either  divided,  shortened,  or 
advanced  for  minus  cyclophoria. 

Plus  cyclophoria  ol  the  right  eye  and  minus  cyclopho- 


21. 


416  CYCLOPHORIA. 

riaof  the  left  eye  (parallel  cyclophoria),  if  uncomplicated, 
calls  for  a  division  of  the  nasal  fibers  of  the  right  superior 
rectus  and  the  temporal  fibers  of  the  left  superior  rectus. 
While  these  operations  would  parallel  the  vertical  axes 
of  the  eyes  with  the  median  plane  of  the  head,  they 
would  develop  a  double  cataphoria.  A  case  of  this  kind, 
complicated  by  right  hyperphoria  and  left  cataphoria, 
calls  for  a  division  of  the  nasal  fibers  of  the  right  su- 
perior rectus  and  the  nasal  fibers  of  the  left  inferior 
rectus. 

The  obliques  themselves  should  never  be  subjected  to 
an  operation  for  cyclophoria;  but,  as  will  be  shown  in 
the  next  chapter,  the  inferior  oblique  may  be  divided 
when  there  is  plus  cyclotropia. 


CHAPTER  VIII. 


COMPENSATING  CYCLOTROPIA. 


THE  law  governing-  the  oblique  muscles  is  that  they 
must  keep  the  vertical  axes  of  the  two  eyes  parallel 
with  the  median  plane  of  the  head.  They  do  this  in 
obedience  to  the  unalterable  law  of  corresponding-  retinal 
points,  and  must  do  it  in  all  states  of  refraction  not 
causing-  a  displacement,  in  opposite  directions,  of  the  two 
retinal  imag-es  as  related  to  the  one  object.  They  must 
also  maintain  this  parallelism  of  the  vertical  axes  in 
those  eyes  whose  refractive  condition  displaces  both  im- 
ag-es,  but  in  the  same  direction  and  to  the  same  extent. 
In  emmetropia,  hyperopia,  and  myopia  there  is  no  dis- 
placement of  imag-es;  hence  the  law  of  corresponding- 
retinal  points  is  satisfied  when  the  obliques  obey  the 
subordinate  law  governing-  them  —  that  is,  when  they 
parallel  the  vertical  axes  with  the  median  plane  of  the 
head.  In  vertical  and  horizontal  astig-matism  there  is 
no  displacement  of  imag-es  of  vertical  and  horizontal 
lines — lines  that  are  parallel  with  the  two  principal  me- 
ridians— while  imag-es  of  oblique  lines  are  displaced,  but 

(417) 


418  COMPENSATING   CYCLOTROPIA. 

in  the  same  direction  and  to  the  same  extent  in  the  two 
eyes;  hence  the  law  of  corresponding-  retinal  points  can 
be  satisfied  only  when  the  subordinate  law  governing1  the 
obliques  is  obeyed. 

In  oblique  astigmatism,  with  the  meridians  of  great- 
est curvature  either  diverging1  or  converging-  above,  the 
imag-es  of  vertical  and  horizontal  lines  are  displaced  so 
that  they  no  long-er  bear  a  proper  relationship  to  the 
lines  themselves;  hence  the  imag-es  must  fall  on  non- 
corresponding-  retinal  points  —  more  properly,  lines.  In 
such  eyes,  no  line  in  space  can  have  both  imag-es  prop- 
erly related  to  it,  for  a  line  that  would  be  parallel  with 
the  meridian  of  greatest  curvature  of  one  eye  would  not 
be  parallel  with  the  meridian  of  greatest  curvature  of 
the  other;  therefore,  while  in  the  former  the  line  and 
its  image  would  be  properly  related,  in  the  latter  this 
could  not  be,  for  the  imag-e  would  be  displaced.  The 
two  imag-es  of  no  line  can  fall  on  corresponding-  retinal 
parts  when,  in  oblique  astig-matism,  the  meridians  of 
greatest  curvature  are  not  parallel.  To  harmonize  these 
images,  and  satisfy  as  best  possible,  but  never  perfectly, 
the  law  of  corresponding  retinal  points,  the  individual  law 
governing  the  obliques  must  be  suspended,  and  the  ver- 
tical axes  of  the  eyes  must  be  made  to  either  converge  or 
diverge  above — the  former  if  the  meridians  of  greatest 
curvature  diverge  above,  the  latter  if  these  meridians 


COMPENSATING  CYCLOTROPIA.          419 

converg-e  above.  The  same  is  true  when  the  principal 
meridians  of  one  eye  are  vertical  and  horizontal,  while 
those  of  the  other  are  oblique. 

While  there  seems  to  be  no  one  who  now  doubts  that, 
in  astigmatism,  there  is  displacement  of  the  images  of 
all  lines  not  parallel  with  the  one  or  the  other  of  the 
two  principal  meridians,  it  will  not  be  out  of  place  here 
to  present  some  incontrovertible  demonstrations,  show- 
ing- that  these  displacements  are  always  toward  the  me- 
ridian of  greatest  curvature. 

The  accompanying  illustrations  are  simple,  are  easily 
understood,  and  are  at  the  same  time  correct.  These,  at  a 
glance,  make  clear  what  has  been  taught  since  1891  con- 
cerning the  obliquity  of  retinal  images  in  oblique  astig- 
matism. Criticism  of  this  teaching  would  not  have  been 
made  if  the  author  had  thought  to  use  these  illustrations 
in  his  first  publication.* 

In  justice  to  Dr.  P.  C.  Hotz,  of  Chicago,  it  must  be 
stated  here  that  he  gracefully  retracted  his  criticism, 
which  was  most  severe,  and  showed  before  the  Chicago 
Ophthalmological  Society  how  it  was  that  he  was  led 
into  the  error  that  formed  the  basis  of  his  criticism.  It 
was  before  this  society  that  he  thought  t  he  had  demon- 
strated that  oblique  astigmatism  did  not  cause  any  dis- 
placement of  the  retinal  image  of  a  vertical  or  horizontal 

*See  Ophthalmic  Record,  Vol.  I.,  No.  1,  1891. 


420  COMPENSATING   CYCLOTROPIA. 

line.  He  used  for  this  purpose  a  camera,  the  lens  of 
which  he  had  rendered  astigmatic  by  adding  a  cylinder 
with  its  axis  at  45°.  On  the  ground  glass  of  his  camera 
he  focused  the  image  of  a  horizontal  line.  This  image 
he  believed  to  be  horizontal,  as  did  all  who  saw  his  dem- 
onstration, but  it  was  not.  With  the  same  camera,  he 
later  focused  the  images  of  two  lines  crossing  each  other 
at  right  angles — the  one  line,  vertical;  the  other,  horizon- 
tal. These  images  were  readily  seen  displaced,  in  oppo- 
site directions,  so  that  the  angles  formed  at  their  point  of 
crossing  were  not  right  angles.  These  two  lines  enabled 
the  camera  to  magnify  the  truth  so  as  to  enable  Hotz 
and  his  fellow-members  of  the  Ophthalmological  Society 
to  see  the  error  into  which  he  had  led  them  at  a  pre- 
vious meeting.  Hotz  was  kind  enough  to  invite  the 
author,  whom  he  had  formerly  criticised,  to  be  present 
at  his  last  demonstration  and  speak  on  oblique  astig- 
matism. 

Dr.  Harold  Wilson  (of  Detroit),  another  critic,  was 
later  forced  to  yield  to  the  argument  of  his  camera  ren- 
dered astigmatic,  which  he  had  focused  on  a  church  spire. 
He  thought  that  the  spire  in  the  photograph  was  vertical, 
and  so  published.  Later  he  studied  both  the  axis  of  the 
spire  and  the  base-line,  and  found  that  the  photograph 
did  not  show  them  to  be  at  right  angles;  that  these 
were  both  inclined  in  opposite  directions.  His  error  in 


COMPENSATING  CYCLOTROPIA. 


421 


observing  only  one  line  was  very  similar  to  the  one  into 
which  Hotz  had  fallen. 

But  to  a  study  of  the  illustrations: 

Fig.  55  is  complex,  showing  a  square  as  seen  by  a  non- 
astigmatic  eye,  as  seen  by  an  eye  astigmatic  according 

a"  Of  d' 


Fig-  55- 

to  the  rule,  and  as  seen  by  the  latter  after  the  astigma- 
tism  has  been  corrected  by  a  plus  cylinder.  The  rec- 
tangie  a-b-c-d  is  the  square  seen  by  the  non-astigmatic 
eye,  and  a-c  and  d-b  show  the  diagonals  of  this  square. 
The  rectangle  a'-b'-c'-d'  is  the  figure  seen  by  the  astig- 
matic eye  with  the  meridian  of  greatest  curvature  verti- 


422  COMPENSATING    CYCLOTROPIA. 

cal.  The  axial  rays  from  the  ends  of  the  lines  a-b  and  d-c 
enter  the  eye  through  parts  of  the  cornea  parallel  with 
the  meridian  of  greatest  curvature  and  so  near  to  it  that 
their  refractive  power  is  practically  the  same.  The  re- 
fraction of  these  axial  rays  from  a  and  b,  by  the  cornea, 
is  such  as  to  make  them  cross  each  other,  on  their  way 
back  to  the  retina,  sooner  than  they  would  have  done  if 
there  had  been  no  astigmatism;  hence  their  points  of 
impingement  on  the  retina  are  more  widely  separated, 
and  the  line  itself  must  be  proportionately  increased. 
The  same  is  true  of  the  axial  rays  from  the  ends  of  the 
line  d-c.  Hence  it  is  clear  that  the  line  a-b  must  become 
the  line  a'-b'  and  the  line  d-c  must  become  the  line  d'-c1. 
Because  of  the  increase  of  the  length  of  the  line  a-b  and 
d-c  the  lines  a-d  and  b-c  are  more  widely  separated,  be- 
coming lines  a'-d'  and  b'-c',  and  we  have — not  a  square, 
but — the  rectangular  parallelogram  a'-b'-c'-d'.  The  di- 
agonal a-c  has  been  rotated  toward  the  vertical  and  be- 
comes a'-c' ;  and  the  diagonal  d-b  has  been  rotated  in  the 
opposite  direction,  but  also  toward  the  vertical,  and  be- 
comes d'-b' .  They  have  both  been  rotated,  by  the  refrac- 
tion of  the  astigmatic  cornea,  toward  the  meridian  of 
greatest  curvature.  The  image  changes  effected  by  the 
astigmatic  cornea  are,  as  shown  in  the  figure:  an  in- 
crease in  the  length  of  the  lines  parallel  with  the  merid- 
ian of  greatest  curvature,  an  increase  in  the  distance 


COMPENSATING  CYCLOTROPIA.          423 

between  the  lines  parallel  with  the  meridian  of  least 
curvature,  and  a  corresponding  rotation  of  the  diago- 
nals toward  the  meridian  of  greatest  curvature.  The 
proper  plus  cylinder  placed  before  this  eye  gives  such 
aid  to  the  least  curved  meridian  of  the  cornea  as  to 
make  its  refractive  power  exactly  equal  to  the  unaided 
refractive  power  of  the  meridian  of  greatest  curvature. 
The  result  will  be  a  lengthening  of  the  horizontal  lines 
a'-d'  and  d'-c'  into  the  lines  a"-d"  and  b"-c"  and  a  dis- 
placement of  the  lines  a'-b'  and  d'-c'  until  they  become 
a"-b"  and  d"-c".  Since  two  of  the  sides  (a-b  and  d-c} 
of  the  square  have  been  lengthened  by  the  astigmatism 
and  the  remaining  two  sides  (a-d  and  b-c)  have  been 
lengthened  to  exactly  the  same  extent  by  the  correct 
plus  cylinder,  the  figure  a"-b"-c"-d" ,  seen  by  the  cor- 
rected astigmatic  eye,  is  a  square.  The  cylinder,  in 
changing  the  rectangular  parallelogram  a'-b' -d-d'  to  the 
square  a"-b"-c"-d",  has  also  rotated  the  diagonals  a'-c' 
and  d'-b'  back  to  their  original  positions;  for  the  diagonal 
a'  '-c' '  coincides  with  the  diagonal  a-c,  and  the  diagonal 
d"-b"  coincides  with  d-b. 

If  the  astigmatism  had  been  corrected  by  a  minus 
cylinder,  the  lines  a'-b'  and  d'-c'  would  have  been  short- 
ened into  the  lines  a-b  and  d-c;  the  lines  a'-d'  and  b'-c1 
would  have  been  brought  closer  together,  a'-d'  becoming 
a-d  and  b'-c!  becoming  b-c;  and  the  diagonals  a'-c?  and 


424  COMPENSATING    CYCLOTROPIA. 

d'-b'  would  have  been  rotated  back  into  the  diagonals  a-c 
and  d-b,  respectively,  so  that  the  figure  thus  seen  would 
be  the  square  a-b-c-d.  Thus  it  is  shown  that  an  astig- 
matic eye,  corrected  with  a  minus  cylinder,  sees  the 
square  with  the  same  measurements  as  that  seen  by  the 
non-astigmatic  eye;  while  the  square  seen  by  the  astig- 
matic eye,  corrected  with  a  plus  cylinder,  is  magnified. 

Turning  the  right  side  of  Fig.  55  up,  it  shows  the  im- 
age changes  when  the  meridian  of  greatest  curvature  is 
horizontal.  In  either  case  the  lines  parallel  with  the 
meridian  of  greatest  curvature  are  made  longer  by  the 
astigmatism,  with  a  corresponding  increase  of  distance 
between  the  lines  parallel  with  the  meridian  of  least 
curvature,  and  the  diagonals  are  rotated  toward  the 
meridian  of  greatest  curvature. 

If  there  is  astigmatism  of  one  eye  with  the  meridian 
of  greatest  curvature  vertical  and  astigmatism  of  the 
same  kind  in  the  other  with  the  meridian  of  greatest 
curvature  horizontal,  the  former  would  see  a  square 
changed  into  a  rectangular  parallelogram,  with  the  longer 
sides  vertical;  while  the  latter  would  see  the  square 
similarly  changed,  but  with  the  longer  sides  horizontal. 
The  images  in  such  eyes  would  be  dissimilar  and  could 
not  be  perfectly  fused;  correcting  cylinders  would  make 
the  images  alike  and  thus  make  complete  fusion  possible. 

What  is  true  of  squares  is  true  of  rectangular  paral- 


COMPENSATING  CYCLOTROPIA. 


425 


lelograms,  as  shown  by  Fig.  56  in  .which  there  is  the 
same  proportionate  lengthening-  of  two  of  the  sides  by 
the  astigmatism,  and  of  the  other  two  sides  by  the  astig- 
matic correction  with  plus  cylinders,  also  the  same  char- 


Fig.  56. 

acter  of  rotations  of  the  diagonals,  the  principal  merid- 
ians being"  vertical  and  horizontal. 

Fig.  57  shows  the  image  changes  when  the  astigma- 
tism is  oblique,  the  meridian  of  greatest  curvature  be- 
ing at  135°.  That  part  of  the  complex  figure  shown  by 
a-b-c-d  is  a  square  as  seen  by  a  non-astigmatic  eye. 
L/ooked  at  by  the  oblique  astigmatic  eye  already  men- 
tioned, the  diagonal  a-c,  being  at  an  angle  of  135°,  is  in  a 
plane  with  the  meridian  of  greatest  curvature,  while  the 
diagonal  d-b  is  in  a  plane  with  the  meridian  of  least 
curvature.  For  reasons  already  given  in  discussing 


426 


COMPENSATING  CYCLOTROPIA. 


Fig.  55,  the  diagonal  a-c  is  increased  in  length  by  the 
astigmatism  into  a'-c' ,  while  the  diagonal  d-b  is  neither 
altered  in  length  nor  in  direction.  The  sides  of  the  square, 
not  being  parallel  with  the  principal  meridians,  must  be 
rotated  toward  the  meridian  of  greatest  curvature,  a-b 


Fig-  57- 

becoming  a'-b,  a-d  becoming  a'-d^  b-c  becoming  b-c',  and 
d-c  becoming  d-d '.  The  figure  a'-b-d-d  is  a  non-rectan- 
gular parallelogram  leaning  down  and  to  the  right.  A 
plus  cylinder  correcting  -  the  astigmatism  will  increase 
the  length  of  diagonal  d-b  into  d'-b'  to  exactly  the  length 
of  the  diagonal  a'-J  and  at  the  same  time  will  rotate  the 


COMPENSATING    CYCLOTROPIA.  427 

lines  a'-b  to  a'-b',  a'-d  to  a'-d',  c'-b  to  c'-b',  and  c'-d  to 
c'-d ',  thus  converting  the  non-rectangular  parallelogram 
a'-b-d-d  into  the  magnified  square  a'-b' -c'-d'. 

Turning  the  right  side  of  Fig.  57  up,  the  image  changes 
are  shown  when  the  meridian  of  greatest  curvature  is  at 
45°.  It  is  clear  that,  if  the  astigmatism  is  equal  and  of 


Fig.  58- 


the  same  kind  in  the  two  eyes,  the  meridians  of  greatest 
curvature  being  parallel,  though  oblique,  the  two  images 
of  a  square  held  vertically  will  be  distorted  alike,  and 
hence  will  fuse  readily  and  completely.  If  the  meridian 
of  greatest  curvature  in  the  right  eye  is  at  135°,  and  in 
the  left  eye  at  45°,  the  image  in  each  eye  will  be  a  non- 


428  COMPENSATING   CYCLOTROPIA. 

rectangular  parallelogram  leaning  in  the  opposite  direc- 
tion from  the  image  in  the  other  eye;  and  the  two  cannot 
be  perfectly  fused,  though  an  attempt  at  fusion  will  be 
made,  in  an  effort  on  the  part  of  the  eyes  to  obey  the 
supreme  law  of  binocular  single  vision,  the  law  of  cor- 
responding retinal  points. 

Fig.  58  shows  how  the  fusion  of  the  images  would 
make  the  square  appear.  This  fusion  is  effected  by  the 
superior  obliques  converging  the  vertical  axes  of  the  eyes. 

Soon  after  Hotz  and  Wilson  had  tried  the  camera  and 
had  published  their  conclusions  unfavorable  to  the  dis- 
tortion of  retinal  images  by  oblique  astigmatism,  Dr. 
Perry,  of  Oneida,  N.  Y.,  betook  himself  to  the  camera, 
with  the  result  shown  in  the  accompanying  half-tone 
cut,  Fig.  59: 

Dr.  Perry's  own  words,  descriptive  of  this  cut,  are  as 
follows : 

"Fig.  59  was  produced  by  taking  a  photograph  of  the 
graduated  circle  with  printed  words  as  shown;  and  then, 
without  moving  camera  or  object,  placing  a  .50  D  cylin- 
drical lens  in  front  of  the  objective  and  exposing  a  sec- 
ond negative,  and,  when  the  photographs  were  finished, 
cutting  away  the  outer  circle  from  the  astigmatic  print 
and  pasting  it  over  the  other  in  such  a  way  as  to  make 
the  horizontal  and  vertical  lines,  respectively,  coincide  on 
the  two  prints.  If  the  cut  is  held  so  that  the  line  of  the 


Fig.  59- 


430  COMPENSATING    CYCLOTROPIA. 

print  reading-  'Astigmatism  Oblique,  135°,'  is  horizontal, 
it  will  be  observed  that  the  distortion  of  the  field  is  such 
that  this  particular  line  is  moved  along  the  scale  nearly 
two  degrees,  while  the  line  which  is  perpendicular  to  it 
is  moved  an  equal  distance,  but  in  a  contrary  direction. 
This  shows  what  must  happen  to  a  retinal  image  in  ob- 
lique astigmatism." 

Dr.  Lowry,  at  the  time  a  private  student  of  the  au- 
thor, was  incited  by  the  published  criticisms  of  Hotz 
and  Wilson  to  use  his  camera.  Half-tone  cuts  were  made 
from  his  photographs,  and,  notwithstanding  these  speak 
for  themselves,  his  descriptive  text  is  here  reproduced: 

"It  has  often  been  noted  that  the  camera  obscura  is 
very  strikingly  similar,  in  its  mechanism,  to  the  human 
eye.  In  this  simple  optical  instrument  we  have  a  me- 
chanical eye,  so  far  as  refraction  is  concerned.  If  we 
compare  to  the  eye  the  component  parts  of  the  photo- 
graphic camera,  which  is  merely  a  camera  obscura  with 
a  device  for  receiving  the  image  on  a  sensitized  plate,  we 
find  the  refractive  media  of  the  former  correspond  to  the 
photographic  lens;  the  iris,  to  the  stop;  the  accommo- 
dation, to  the  focusing  apparatus;  and  the  retina,  to  the 
ground  glass.  Focus  the  camera  properly,  and  we  have 
the  emmetropic  eye.  By  placing  a  concave  cylindrical 
lens,  axis  at  90°,  in  apposition  to  the  photographic  lens, 
we  have  simple  hypermetropic  astigmatism  according  to 


COMPENSATING    CYCJUOTKOPIA. 


431 


the  rule;  if  we  place  the  axis  at  180°,  we  have  simple  hy- 
permetropic  astigmatism  against  the  rule;  if  we  place 
the  axis  anywhere  between  the  \ertical  and  horizontal, 


Fig.  60. 

we  get  oblique  astigmatism.     Whether  or  not  the  image 
will  be  oblique  on  the  ground  glass  will  be  seen  later. 

"To  illustrate  these  points,  I  have  made  the  accompa- 
nying- photographs  with  a  rapid  rectilinear  lens,  used  in 
the  Rochester  Optical  Company's  5x7  midget  camera. 
The  camera  was  not  moved  or  changed  in  any  way  foi 


432 


COMPENSATING  CYCLOTROPIA. 


the  first  five  photographs.  Fig1.  65  was  made  at  another 
time.  The  rectangle  was  made  mathematically  accurate 
on  a  piece  of  cardboard  24  x  30.  The  lines,  one  inch  wide, 


Fig.  61. 

are  prolonged  beyond  the  rectangle  to  show  more  clearly 
the  obliquity  of  imagfes  that  may  be  produced  by  the 
cylinders  obliquely  placed.  The  watch  is  used  as  a 
plumb,  and  is  seen  in  the  same  position  in  all.  The 
photographs  are  not  inverted  as  the  images  \vould  be  on 
the  ground  glass  or  the  retina. 


COMPENSATING   CYCLOTROPIA. 


433 


"In  Fig.  60,  no  cylindrical  lens  is  used,  and  we  get 
a  perfect  rectangle,  sharp  and  distinct  in  its  outline,  as 
would  be  seen  by  an  emmetropic  eye. 


Fig.  62. 

"In  making  Fig.  61  a  minus  3  D.  cylindrical  lens  is 
placed  just  in  front  of,  and  in  apposition  to,  the  photo- 
graphic lens,  with  its  axis  at  45°.  *  A  plus  1.50  D  spher- 
ical lens  is  used  with  the  cylinder  in  order  to  give  the 


*  These  prints  are  all  the  reverse  o 
it  would  be  seen. — AUTHOR. 


f  the  images,  therefore  the  reverse  of  the  object  as 


434 


COMPENSATING  CYCLOTROPIA. 


middle  of  the  focal  interval  without  changing-  the  camera. 
In  this  the  vertical  and  horizontal  lines  are  equally  indis- 
tinct. The  vertical  lines  deviate  to  the  left  at  the  top, 


»"•»"/ 


Fig.  63. 

and  to  the  right  at  the  bottom,  while  the  horizontal  lines 
are  depressed  at  the  right  and  elevated  at  the  left.  T^ne 
plumb  shows  that  the  card  is  in  just  the  same  position 
as  in  Fig.  60,  and  the  camera  has  not  been  moved  from 
its  original  position.  This  picture  is  clearly  a  non-rec- 
tangular parallelogram. 


COMPENSATING    CYCLOTROPIA. 


435 


"  If  the  axis  of  the  cylinder  be  changed  to  90°,  we  get 
Fig.  62,  which  represents  simple  vertical  hypermetropic 
astigmatism.  This  is  made  without  the  plus  1.50  D  sphere 
and  without  the  camera's  being  changed  in  the  least  from 


Fig.  64. 

its  position  in  Fig.  60  and  Fig.  61.  The  meridian  of  great- 
est curvature  here  is  at  90°,  with  the  least  at  180°.  It  is 
a  perfect  rectangle,  with  its  horizontal  lines  sharply  cut 
and  the  vertical  very  indistinct. 

"Now  if  we  place  the  axis  of  the  cylinder  at  135°, 
again  adding  the  plus  1.50  D  sphere,  a  non-rectangular 


436  COMPENSATING   CYCLOTROPIA. 

parallelogram  is  formed  with  its  sides  deviating-  in  the 
opposite  direction  to  those  in  Fig-.  61.  This  is  shown  in 
Fig-.  63.  Every  part  is  equally  indistinct,  and  nowhere 
are  the  lines  at  right  angles  as  in  the  original. 


Fig.  65. 

"  By  placing  the  axis  of  the  cylinder  at  180°,  without 
the  plus  1.50  D  sphere,  we  produce  simple  hypermetropic 
horizontal  astigmatism,  the  effect  of  which  is  illustrated 
in  Fig.  64.  Here  we  have  the  meridian  of  greatest  curva- 
ture at  180°,  and  the  least  at  90°.  We  obtain  a  perfect 


COMPENSATING    CYCLOTROPIA.  437 

rectangle,  with  its  vertical  lines  clear  and  its  horizontal 
very  indistinct,  in  contradistinction  to  Fig.  62. 

"Fig1.  65  is  the  same  as  Fig1.  61  without  the  plus  1.50  D 
sphere  to  give  the  focal  interval,  nor  is  the  camera  re- 
focused  to  give  it.  This  photograph  was  made  at  a  dif- 
ferent time,  and  the  camera  was  not  in  exactly  the  same 
position  as  for  the  other  five.  An  eye  with  the  meridian 
of  greatest  curvature  at  45°  and  3  D  of  simple  hyper- 
metropic  astigmatism  would  see  the  object  as  shown 
in  this  figure,  if,  under  the  influence  of  a  mydriatic  or 
in  old  age,  it  were  relieved  of  all  ciliary  action.  The 
rhomboidal  figures  are  seen  very  clearly  here  at  the 
angles  and  on  the  watch. 

"  Suppose  one  of  the  meridians  of  greatest  curvature 
to  be  at  45°,  and  the  other  at  135°,  one  image  would  be 
seen  as  in  Fig1.  61,  and  the  other  as  in  Fig-.  63;  in  obedi- 
ence to  the  law  of  corresponding-  retinal  points,  we  would 
have  these  two  fig-ures  superimposed,  forming-  a  trape- 
zoid.  If  the  meridians  diverged  above,  we  would  have 
the  long-  side  above,  and  the  short  side  below.  In  this 
form  of  astigmatism  we  would  not  only  have  a  ciliary 
strain,  but  the  superior  obliques  would  make  an  attempt 
to  bring  the  harmonizing  parts  of  the  two  retinas  under 
the  dissimilar -images  in  order  to  have  a  single  object.  If 
the  meridians  converged  above,  the  short  side  of  the  trape- 
Zoid  would  be  above,  and  the  long  side  below.  This  fu- 


438  COMPENSATING   CYCLOTROPIA. 

sion  of  dissimilar  parallelograms  into  a  trapezoid,  long- 
side  below,  would  be  effected  by  the  inferior  obliques. 

"But  the  bone  of  contention  has  been  principally  the 
question  of  the  deviation  or  the  non-deviation  of  the  image 
on  the  retina  in  oblique  astigmatism.  Others  have  proved 
it  by  the  laws  of  optics,  by  clinical  experience,  and  by 
logical  reasoning;  and  it  seems  to  me  that  my  pho- 
tographic demonstrations  have  added  very  conclusive 
evidence  to  the  theory  that,  in  oblique  astigmatism,  the 
retinal  images  of  vertical  and  horizontal  objects  deviate 
from  their  normal  direction." 

Since  1887,  it  has  been  taught  that,  in  oblique  as- 
tigmatism, abnormal  work  is  required  of  the  obliques. 
However,  it  was  not  until  1891  that  the  cause  of  this  ab- 
normal action  on  the  part  of  the  obliques  was  discovered 
to  be  a  want  of  parallelism  of  the  meridians  of  greatest 
curvature  of  the  corneas  and  a  consequent  dissimilar  dis- 
tortion of  retinal  images.  It  was  then  announced  that, 
in  oblique  astigmatism,  be  the  obliquity  much  or  little, 
it  is  a  physical  impossibility  for  a  horizontal  line  and  its 
retinal  image  to  lie  in  the  same  plane.*  The  same  is 
true  of  all  lines  not  parallel  with  one  or  the  other  of  the 
two  principal  meridians. 

The  obliquity  of  retinal  images  was  first  demonstrated, 
in  the  latter  part  of  1890,  by  the  production  of  artificial 

*See  Ophthalmic  Record,  Vol.  I.,  No.  1. 


COMPENSATING  CYCLOTROPIA. 


439 


oblique  astigmatism,  at  which  time  the  following  law 
was  formulated:  "  The  retinal  image  is  displaced  toward 
the  meridian  of  greatest  curvature"  This  being  true — 
and  there  is  no  exception  to  this  rule — the  image  of  a  ver- 
tical or  horizontal  line  is  displaced  toward  the  meridian 
of  best  curvature  in  oblique  hyperopic  astigmatism,  from 
the  best  meridian  in  oblique  myopic  astigmatism,  and  to- 
ward the  myopic  meridian  in  oblique  mixed  astigmatism. 


RIGHT  LEFT 

Fig.  66. 

As  a  result  of  the  experiments  with  artificially  pro- 
duced astigmatism,  the  next  eight  figures  were  con- 
structed, some  of  them  showing  the  character  of  the 
images  of  a  horizontal  arrow,  formed  on  the  two  retinas; 
while  other  of  these  figures  show  clearly  the  compensat- 
ing cyclotropia  made  necessary  that  the  images  might  be 
fused.  This  cyclotropia  corresponds  with  the  compen- 
sating esotropia  which  occurs  when  both  images  are  dis- 


440          COMPENSATING  CYCLOTROPIA. 

placed  by  prisms  with  their  bases  out;  with  the  compen- 
sating' exotropia,  when  images  are  displaced  by  prisms 
with  their  bases  in;  with  the  compensating-  hypertropia 
of  one  eye  and  catatropia  of  the  other,  when  a  prism  is 
base  down  before  one  eye  and  base  up  before  the  other. 
In  either  case,  the  turning1  must  occur  in  obedience  to  the 
supreme  law  of  binocular  single  vision,  the  law  of  cor- 
responding- retinal  points. 

Fig-.  66  represents  a  pair  of  eyes  in  which  the  two 
principal  meridians  are  vertical  and  horizontal  (they  can 
also  represent  eyes  that  are  non-astigrnatic).  If  an 
arrow,  or  the  picture  of  an  arrow,  be  held  horizontally 
before  these  eyes,  the  arrow-head  toward  the  patient's 
left  eye,  it  will  throw  a  reversed  imag'e  on  each  retina, 
and  the  two  images  will  be  in  the  same  plane  with  the 
object.  These  two  imag-es  fall  on  parts  of  the  two 
retinas  that  act  tog-ether;  hence,  but  one  object  is  seen. 

Fig".  67  represents  a  pair  of  eyes  in  which  there  is  hy- 
peropic  astig-matism,  either  simple  or  compound.  The 
left  eye  has  its  best  meridian  vertical.  In  this  eye  the 
arrow,  held  as  before,  throws  its  image  on  the  horizontal 
meridian  of  the  retina,  hence  in  the  same  plane  with  it. 
In  the  rig-ht  eye  the  best  meridian  is  at  135°,  as  shown 
by  the  dotted  line.  In  obedience  to  the  well-known  law 
of  refraction  by  curved  surfaces,  the  imag-e  of  the  same 
arrow  must  be  oblique  in  this  eye,  and,  hence,  not  in  the 


COMPENSATING    CYCLOTROPIA. 


441 


same  plane  with  the  object.  The  obliquity  of  the  image 
will  be  greater  or  less,  depending-  on  the  quantity  of  the 
astigmatism.  It  is  represented  as  falling1  on  meridian 
170°  of  the  retina.  The  horizontal  image  in  the  left  eye 


RIGHT 


Fig.  67. 


LEFT 


and  the  oblique  image  in  the  right  eye  do  not  fall  on 
parts  of  the  two  retinas  that  harmonize.  The  direction 
of  either  image  in  relation  to  the  other  cannot  be  changed 
except  by  artificial  means — a  proper  cylindrical  lens. 


Fig.  68. 


This  being-  true,  the  pair  of  unaided  astigmatic  eyes, 
represented  by  Fig.  67,  must  see  the  arrow  double,  as 
shown  in  Fig.  68,  unless  something  is  done  by  the  eyes 
themselves  for  the  purpose  of  harmonizing  the  images. 


442  COMPENSATING    CYCLOTROPIA. 

In  all  cases  of  oblique  astigmatism,  unless  the  obliquity 
is  in  the  same  direction  in  the  two  eyes,  and  the  astig- 
matism the  same  in  kind  and  quantity,  something1  must 
be  done  in  order  to  prevent  double  vision,  as  represented 
in  Fig1.  68.  There  are  but  two  ways  of  accounting-  for 
the  absence  of  this  peculiar  kind  of  double  vision  in  such 
forms  of  astigmatism  as  that  represented  in  Fig".  67. 
Sectional  ciliary  contraction  would  account  for  it.  If  it 
were  possible  for  the  ciliary  muscle  thus  to  act,  one  can 
readily  understand  how  the  curvature  of  the  lens  could 
be  so  changed  as  to  result  in  lenticular  astigmatism 
equal,  but  at  right  angles,  to  the  corneal  astigmatism. 
If  such  ciliary  action  were  to  take  place  in  the  right  eye 
of  Fig.  67,  the  retinal  image  would  not  only  be  made  as 
sharp  as  if  in  an  emmetropic  eye,  but  it  would  also  be 
made  to  lose  its  obliquity,  and  thus  double  vision  would 
be  prevented.  As  beautifully  as  this  sectional  ciliary 
action  would  account  for  the  absence  of  double  vision 
in  cases  of  oblique  astigmatism,  it  is  certainly  a  false 
theory,  since,  when  all  ciliary  power  has  been  suspended 
by  atropine  or  age,  the  eyes  are  still  able  to  do  something 
by  means  of  which  the  double  vision  represented  by  Fig. 
68  is  prevented. 

There  must  be  double  vision,  unless  the  oblique  image 
in  the  right  eye  and  the  horizontal  image  in  the  left  eye 
can  be  made  to  occupy  corresponding  parts  of  the  two 


COMPENSATING  CYCLOTROPIA. 


443 


retinas.     This  could  be  effected  easily  by  the  harmonious 
symmetrical  action  of  the  superior  oblique  muscles. 

Fig.  69  shows  how  the  eyes  represented  by  Fig.  67  act 
in  order  to  have  the  images  fall  on  corresponding  parts  of 
the  retinas.  The  superior  oblique  muscle  of  the  right 
eye  has  so  revolved  it  as  to  bring  meridian  175°  of  the 
retina  in  position  to  receive  the  impress  of  the  oblique 
image;  while,  at  the  same  moment,  the  superior  oblique 


RIGHT 


Fig.  69. 


LEFT 


muscle  of  the  left  eye  has  so  revolved  it  as  to  bring  me- 
ridian 175°  to  the  horizontal,  hence  in  position  to  receive 
the  horizontal  image.  The  oblique  and  horizontal  im- 
ages being  now  on  harmonizing  portions  of  the  retinas, 
there  is  no  double  vision. 

Fig.  70  represents  a  pair  of  hyperopic  astigmatic  eyes, 
the  left  one  having  its  best  meridian  vertical  and  the 
right  one  having  its  best  meridian  at  45°.  In  these  eyes 


444 


COMPENSATING  CYCLOTROPIA. 


there  are  a  left  horizontal  image  (image  and  arrow  in  same 
plane)  and  a  right  oblique  image,  this  time  on  retinal 
meridian  10°.  Nothing  but  artificial  means  will  change 
the  relative  direction  of  these  images;  and  there  must  be 
double  vision,  unless  the  oblique  image  can  be  made  to 
fall  on  a  portion  of  the  retina  that  will  harmonize  with 
that  portion  of  the  other  retina  on  which  the  horizontal 
image  may  fall. 


RIGHT 


LEFT 


Fig.  70. 


The  double  vision  that  would  exist  in  astigmatic  eyes 
represented  in  Fig.  70  is  prevented  by  the  harmonious 
action  of  the  inferior  oblique  muscles,  as  shown  by  Fig. 
71,  the  inferior  oblique  of  the  right  eye  bringing  meridian 
5°  under  the  oblique  image,  while  the  inferior  oblique  of 
the  left  eye  causes  meridian  5°  to  come  under  the  hori- 
zontal image.  Thus  the  two  images  are  made  to  fall  on 
corresponding  parts  of  the  two  retinas. 


COMPENSATING  CYCLOTROPIA. 


445 


RlSHT 


Fig.  71. 


LETT 


Fig.  72  represents  a  pair  of  hypermetropic  astigmatic 
eyes,  with  half  the  quantity  of  astigmatism  found  in  the 
eyes  represented  by  Fig.  67  and  Fig.  70;  but  in  both  eyes 
the  best  meridian  is  oblique — in  the  left  eye  at  45°,  and  in 
the  right  eye  at  135°.  An  arrow  held  in  the  horizontal 
position  before  these  eyes  will  throw  an  oblique  image  on 
each  retina,  the  one  in  the  left  eye  on  meridian  5°,  and  the 


RI6H 


Fig.  72. 


LEFT 


446 


COMPENSATING  CYCLOTROP1A. 


one  in  the  right  eye  on  meridian  175°.  Without  some 
change  double  vision,  as  shown  in  Fig.  68,  will  be  inevit- 
able. 

In  the  oblique  astigmatism  of  the  two  eyes  represented 
by  Fig.  72,  the  two  oblique  images  are  made  to  fall  on 
corresponding  parts  of  the  two  retinas  by  the  harmonious 
action  of  the  two  superior  oblique  muscles,  as  shown  in 
Fig.  73. 


RIGHT 


.  73- 


The  obliquity  of  the  image  and  the  consequent  strain 
on  the  oblique  muscles  fully  account  for  the  greater 
trouble  attending  oblique  astigmatism  than  is  found 
connected  with  astigmatism  in  the  vertical  or  horizontal. 
As  is  well  known,  non-oblique  myopic  astigmatism  is  un- 
attended by  any  sort  of  ciliary  strain  in  distant  vision. 

In  oblique  myopic  astigmatism,  there  is  strain  on  either 
the  two  superior  or  the  two  inferior  oblique  muscles  in 


COMPENSATING  CYCLOTROPIA.          447 

both  distant  and  near  seeing".  In  all  other  forms  of  non- 
parallel  oblique  astigmatism,  there  is  likewise  strain  on 
the  oblique  muscles. 

In  all  kinds  of  non-oblique  astigmatism,  also  in  simple 
hyperopia,  the  time  comes  when  all  nervous  phenomena 
caused  by  their  existence  pass  away.  Their  disappear- 
ance, being  gradual,  but  finally  complete,  coincides  with 
the  failure  and  final  loss  of  ciliary  power  brought  about 
by  advancing  age.  The  symptoms  caused  by  oblique 
astigmatism  may  be  modified  by  old  age  putting  at  rest 
the  ciliary  muscles;  but  they  cannot  be  made  to  vanish, 
for  the  oblique  muscles  are  forced  to  continue  to  act  in 
age  as  in  youth,  so  as  to  harmonize  the  images  on  the 
two  retinas. 

The  plates  made  to  illustrate  the  paper  read  by  the 
author  at  the  meeting  of  the  Eighth  International  Con- 
gress of  Ophthalmology  (Edinburgh,  1894),  are  both  in- 
teresting and  instructive.  They  are  reproduced  here, 
together  with  the  descriptive  text. 

Plate  I.  represents  a  pair  of  eyes  that  are  non-astig- 
matic; or,  if  astigmatism  exists,  the  principal  meridians 
are  vertical  and  horizontal.  These  eyes  are  represented 
as  looking  at  a  rectangle.  The  line  ep  across  the  right 
eye  is  the  horizontal  meridian,  and  the  line  g~h  is  the 
vertical  meridian,  while  their  point  of  intersection  (5) 
is  the  macula.  Similarly  the  line  ep  in  the  left  eye  rep- 


COMPENSATING  CYCLOTROPIA.         449 

resents  the  horizontal  meridian,  and  gh  represents  the 
vertical  meridian,  their  point  of  intersection  (5)  being-  the 
macula.  The  vertical  meridian  of  the  right  eye  and  that 
of  the  left  eye  are  parallel.  Point  5  in  the  rectangle  is 
the  point  of  fixation.  The  line  5-5  from  the  macula  of 
the  right  e}re  is  the  visual  axis  of  that  eye,  and  likewise 
the  line  5-5  is  the  visual  axis  of  the  left  eye.  These 
intersect  at  point  5  of  the  rectangle. 

According  to  the  well-known  law  of  refraction  by 
curved  surfaces,  such  as  are  now  under  consideration, 
the  rectangular  object  will  throw  a  rectangular  image 
on  each  retina,  the  size  of  which  will  bear  a  definite  pro- 
portion to  the  size  of  the  object.  The  center  of  retinal 
curvature  of  the  right  eye  is  x,  through  which  all  lines 
of  direction  from  this  eye  must  pass.  The  lower  inner 
corner  of  this  image  is  thus  connected  with  the  upper 
right-hand  corner  of  the  object  by  the  line  1-1;  in  the 
same  way  the  upper  inner  corner  of  the  image  is  con- 
nected with  the  lower  right-hand  corner  of  the  object 
by  the  visual  line  2-2;  and  so  on  for  the  other  corners 
of  image  and  object.  In  like  manner  the  corners  of  the 
rectangular  image  in  the  left  eye  may  be  connected  with 
corresponding  corners  of  the  object  by  lines  passing 
through  the  center  of  retinal  curvature  (x)  of  that  eye. 
If  the  left  eye  should  be  excluded,  the  right  eye  would 
see  the  rectangle  1-2-3-4;  if  the  right  eye  should  be 


450          COMPENSATING  CYCLOTROPlA. 

screened,  the  left  eye  would  see  the  same  rectangular  fig- 
ure. Both  eyes  together,  in  obedience  to  both  the  law  of 
corresponding  retinal  points  and  the  law  of  projection, 
would  see  the  one  common  rectangle  1-2-3-4.  The  supe- 
rior and  inferior  recti  in  these  eyes  have  kept  the  visual 
axes  in  the  same  plane,  the  external  and  internal  recti 
have  regulated  their  tension  so  that  they  have  converged 
these  axes  to  the  point  5,  and  the  superior  and  inferior 
obliques  have  kept  the  naturally  vertical  axes  parallel 
with  the  median  plane  of  the  head. 

The  obliques  have  to  perform  only  the  simple  function 
in  oblique  astigmatism,  the  meridians  of  greatest  curva- 
ture being  parallel,  and  the  degree  of  astigmatism  the 
same  in  the  two  eyes;  but  it  would  not  be  possible  for 
such  eyes  to  see  the  rectangle  held  in  the  position  shown 
in  Plate  I.  as  a  rectangle.  L/et  the  meridians  of  greatest 
curvature  be  at  45°  in  the  right  eye  and  also  at  45°  in  the 
left  eye.  As  a  result  of  the  refraction  of  the  astigmatic 
cornea  of  the  right  eye,  the  rectangular  figure  would 
throw  a  parallelogram  image  on  the  retina,  the  image 
inclining  down  and  out.  A  parallelogram  image  would 
be  thrown  on  the  left  retina  also,  and  it  would  incline 
down  and  in.  Looked  at  with  either  eye  alone,  the  rec- 
tangle would  be  seen  as  a  parallelogram  inclined  down 
and  to  the  right;  looked  at  with  both  eyes,  it  would  be 
a  parallelogram  of  the  same  shape  and  inclination  as 


COMPENSATING  CYCLOTROPIA.  451 

seen  by  each  eye  separately.  The  extrinsic  muscles  of 
these  eyes  have  performed  the  same  function  as  the  mus- 
cles of  the  eyes  shown  in  Plate  I.  and  with  the  same  re- 
sult— viz.,  binocular  single  vision.  The  law  of  corre- 
sponding- retinal  points  and  the  law  of  projection  having 
full  sway  in  both  pairs  of  eyes,  the  one  pair  sees  the 
figure  as  it  is — a  rectangle — while  the  other  pair  sees 
the  same  figure,  when  held  in  the  same  position,  as  a 
parallelogram  leaning  down  and  to  the  right.  With  the 
visual  axes  properly  directed  by  the  recti  and  the  verti- 
cal meridians  kept  parallel  by  the  obliques,  the  two 
eyes  are  kept  so  related  that  the  two  images  of  the 
object  looked  at  fall  on  harmonizing  parts  of  the 
two  retinas,  and  the  object  is  necessarily  seen  as  one, 
and  of  the  same  shape  as  when  seen  with  each  eye  sep- 
arately. 

In  any  state  of  refraction  the  relationship  between 
corresponding  points  of  the  two  retinas  is  unalterable. 
It  is  well  known  that,  taken  as  a  whole,  the  nasal  half 
of  one  retina  harmonizes  with  the  temporal  half  of  the 
other,  and  that  all  points  of  either  retina  bear  a  fixed 
and  unalterable  relationship  to  the  macula  and  to  the 
vertical  and  horizontal  meridians.  A  retinal  point  in 
the  nasal  half  of  the  right  retina,  bearing  a  definite  re- 
lationship to  the  macula  and  the  vertical  and  horizontal 
meridians,  must  harmonize  with  a  point  in  the  temporal 


452  COMPENSATING   CYCLOTROPIA. 

half  of  the  left  retina  similarly  located;  and  it  can  har- 
monize with  no  other  retinal  point  under  any  conditions. 

The  complicated  function  of  the  obliques  is  necessary 
in  oblique  astigmatism  when  the  meridians  of  greatest 
curvature  diverge  or  converge  above.  This  is  necessary 
that  they  may  bring  harmonizing  parts  of  the  two  retinas 
under  dissimilar  images,  and  thus  insure  binocular  single 
vision;  but,  as  will  be  shown,  the  object,  though  seen  as 
one,  will  be  distorted. 

Plate  II.  may  be  taken  for  stud}T.  Both  eyes  have 
oblique  astigmatism  of  the  same  kind  and  quantity.  In 
the  right  eye  the  meridian  of  greatest  curvature  is  at 
135°  and  in  the  left  eye  at  45°.  If  the  rectangular  figure 
represented  in  Plate  I.  be  held  in  the  same  position  be- 
fore the  eyes  represented  in  Plate  II.,  it  would  not  be 
seen  with  one  eye  alone  or  with  both  together  as  a  rectan- 
gle. The  rectangle  shown  in  Plate  I.,  when  held  before 
the  right  eye  in  Plate  II.,  instead  of  throwing  a  rec- 
tangular, would  throw  a  non-rectangular,  parallelogram 
image  on  the  right  retina;  the  same  rectangle  would 
also  throw  a  non-rectangular  parallelogram  image  on 
the  left  retina.  The  state  of  refraction  of  the  right  eye 
would  make  the  distorted  image  lean  down  and  toward 
the  left  side,  while  the  distorted  image  in  the  left  eye 
would  lean  down  and  toward  the  right  side.  Cutting 
off  the  view  of  the  left  eye,  the  law  of  direction  would 


(453) 


454         COMPENSATING  CYCLOTROPIA. 

have  full  sway,  while  the  law  of  corresponding-  points 
would  be  suspended.  Since  in  one  eye  alone  the  law  of 
direction  is  unalterable,  all  lines  of  direction  must  cross 
in  the  center  of  retinal  curvature;  and  the  right  eye, 
with  the  parallelogram  image  leaning  down  and  to  the 
left,  must  see  the  figure  casting  the  image,  not  as  a 
rectangle,  but  as  a  parallelogram  leaning  down  and  to 
the  left.  Screening  the  right  eye  while  the  left  eye 
looks  on  the  rectangle,  it  is  seen,  not  as  a  rectangle, 
but  as  a  parallelogram  leaning  down  and  to  the  right, 
the  law  of  direction  determining  the  shape  of  the  figure 
seen  by  the  left  eye,  just  as  it  fixed  the  shape  of  the 
figure  seen  by  the  right  eye.  Fig.  1-2-3-4  is  what  is 
seen  with  the  right  eye  alone;  Fig.  l'-2'-3'-4'  is  what  is 
seen  by  the  left  eye  alone.  The  moment  these  two  eyes 
are  allowed  to  look  at  the  rectangular  figure,  the  law  of 
corresponding  retinal  points  is  brought  into  conflict  with 
the  law  of  direction,  and  the  latter  is  modified  by  the 
former.  There  is  no  necessity  for  changing  the  visual 
axes  when  looking  at  the  rectangle  with  these  two  eyes; 
but,  unless  some  change  is  effected  in  some  way,  each 
eye  would  see  its  own  parallelogram  leaning  down  and 
toward  the  opposite  side.  Instantly  a  change  does  take 
place  in  both  eyes,  so  that  the  two  together  see,  not  a 
rectangle  nor  a  parallelogram,  but  a  trapezoid,  with  the 
longer  side  above.  A  clear  understanding  of  what  this 


COMPENSATING   CYCLOTROPIA.  455 

change  is  and  how  it  is  effected  may  be  had  by  a  further 
study  of  Plate  II.  In  the  right  eye  is  shown  a  dotted 
parallelogram  a-b-c-d,  of  precisely  the  same  form  as  the 
parallelogram  image  1-2-3-4;  but  in  the  former  the  upper 
and  lower  lines  are  parallel  with  the  horizontal  meridian. 
In  the  left  eye  also  is  shown  a  dotted  parallelogram 
a'-b'-c'-d',  of  the  same  form  as  the  parallelogram  l'-2'- 
3'-4',  with  its  upper  and  lower  lines  parallel  with  the 
horizontal  meridian  of  this  eye.  The  line  c-b  in  the  right 
eye  bears  throughout  the  same  relation  to  the  macula, 
the  horizontal  and  vertical  meridians  of  this  eye,  that  the 
line  c'-b'  does  to  the  same  parts  of  the  left  eye,  and  they, 
therefore,  correspond.  The  greater  part  of  the  line  d-a 
in  the  right  eye  also  corresponds  with  the  greater  part 
of  the  line  d'-a'  in  the  left  eye,  the  parts  of  these  lines 
not  corresponding  being  their  extremities.  But  the  line 
c-d  in  the  right  eye  nowhere  corresponds  with  the  line 
c'-df  in  the  left  eye,  except  at  the  points  of  beginning 
above;  and  the  same  is  true  of  lines  b-a  and  d'-a',  in  their 
respective  eyes.  If  the  dotted  parallelograms  could  be 
made  to  coincide  with  the  parallelogram  images,  the  re- 
sult would  be  that  the  two  eyes  together  would  see  the 
figure  a-b-c-d',  a  trapezoid,  with  the  longer  side  above. 
How  this  is  effected  is  shown  in  Plate  III.,  where  each 
eye  has  been  revolved  on  its  visual  axis  by  its  superior 
oblique  muscle,  so  that  the  horizontal  meridian  is  made 


456  COMPENSATING   CYCLOTROPIA. 

parallel  with  the  upper  and  lower  borders  of  the  parallel- 
ogram image;  and  thus,  as  far  as  possible,  correspond- 
ing1 parts  of  the  two  retinas  are  brought  under  the  two 
dissimilar  images,  and  the  figure  seen  binocularl}7"  is 
a-b-c-d'.  The  part  of  this  trapezoid  seen  in  common  by 
the  two  eyes  is  a'-b-c-d,  the  part  seen  by  the  right  eye 
alone  is  a-b-a',  and  that  seen  by  the  left  eye  alone  is 
d-c-d' '.  As  will  be  seen,  the  law  of  corresponding-  points 
has  so  modified  the  law  of  projection  that  the  visual  lines 
no  longer  have  a  common  crossing"  point.  This  is  anarchy, 
so  far  as  projection  is  concerned,  in  these  eyes. 

When  the  law  of  direction  is  interfered  with,  as  a  re- 
sult of  the  conflict  between  it  and  the  more  imperious 
law  of  corresponding-  retinal  points,  the  object  seen  is 
always  in  the  position  that  it  would  have  been  in,  had 
the  images  primarily  fallen  on  the  parts  of  the  two  ret- 
inas that  have  been  rotated  under  them,  in  obedience  to 
the  supreme  law  of  binocular  single  vision — the  law  of 
corresponding  retinal  points.  The  displaced  images,  as  a 
result  of  either  natural  or  artificial  means,  cover  areas  of 
the  two  retinas  that  do  not  correspond.  In  order  to  have 
binocular  single  vision,  retinal  areas  that  more  nearly 
correspond,  and  are  of  the  same  shape  and  size  as  the  im- 
ages, must  be  brought  under  them.  The  object  will  be 
seen  as  though  no  rotation  had  taken  place,  as  if  the  im- 
ages had  primarily  fallen  on  these  parts,  in  perfect  obe- 


(457) 


458         COMPENSATING  CYCLOTROPIA. 

dience  to  the  law  of  projection,  although  the  lines  of  di- 
rection drawn  from  the  images  to  the  single  object  will 
not  cross  at  the  center  of  retinal  curvature.  In  cases  of 
decentration  of  the  maculas,  and  in  displaced  images  by 
means  of  prisms,  all  lines  of  direction  will  cross  at  one 
point,  but  that  point  will  be  above,  below,  to  the  outer 
or  inner  side  of  the  true  point;  while  in  oblique  astigma- 
tism, and  when  the  axes  of  correcting  cylinders  are  dis- 
placed, no  three  lines  of  direction  cross  at  the  same  point. 

In  like  manner  a  plate  could  be  made  showing  how 
astigmatic  eyes,  with  meridians  of  greatest  curvature 
converging  above,  would  see  a  rectangle  distorted  into 
a  trapezoid,  the  longer  side  below.  In  each  eye  there 
would  be  a  parallelogram  image  inclining  down  and  out. 
To  fuse  these  into  a  trapezoid,  the  inferior  oblique  mus- 
cles would  be  brought  into  action,  in  order,  as  far  as 
possible,  to  bring  corresponding  retinal  parts  under  dis- 
similar images,  which  is  done  the  moment  the  obliques 
displace  the  horizontal  meridians  so  that  they  become 
parallel  with  the  upper  and  lower  borders  of  the  dis- 
torted images. 

Imperfect  as  is  binocular  single  vision  in  uncorrected 
oblique  astigmatism,  the  meridians  of  greatest  curvature 
either  diverging  or  converging  above,  it  could  be  effected 
in  no  other  way  than  by  a  revolution  of  the  eyes  by  the 
symmetric  harmonious  action  of  the  oblique  muscles.  It 


COMPENSATING  CYCLOTROPIA.          459 

is  true  that  Nature  has  one  other  method  of  preventing 
diplopia — namely,  mental  suppression  of  one  of  the  dis- 
placed images.  It  may  be  that  amblyopia  resulting-  from 
oblique  astigmatism  high  in  degree,  and  from  insufficiency 
of  the  obliques,  is  more  common  than  one  would  at  first 
think.  Certainly,  if  the  obliques  cannot  do  their  proper 
work  in  effecting  binocular  single  vision,  in  the  first 
years  of  life,  nothing  is  more  reasonable  than  to  suppose 
that  amblyopia  ex  anopsia  would  develop.  Who  has 
not  seen  cases  of  amblyopia  without  being  able  to  ac- 
count for  it  ? 

The  phenomena  outlined  can  be  demonstrated  experi- 
mentally by  any  one  who  desires  to  prove  all  things;  for 
he  can  produce  in  his  own  case,  at  pleasure,  any  form  of  as- 
tigmatism. But  some  may  be  ready  to  say  that  artificial 
astigmatism  is  one  thing  and  natural  astigmatism  is  an- 
other thing.  This  is  true,  but  only  in  name.  That  3  D 
of  artificial  hyperopic  astigmatism  is  the  same  error  of 
refraction  as  3  D  of  natural  hyperopic  astigmatism  is 
abundantly  proved  by  the  fact  that  each  is  thoroughly 
corrected  by  a  plus  3  cylinder,  axis  properly  placed. 
Either  plus  or  minus  cylinders  may  be  used  in  the  ex- 
periments, for  the  one  is  as  capable  of  producing  arti- 
ficial astigmatism  as  the  other.  If  the  plus  cylinders 
(3  D)  be  used,  the  astigmatism  produced  has  its  meridian 
of  greatest  curvature  at  right  angles  to  the  axis  of  the 


460  COMPENSATING   CYCLOTROPIA. 

cylinder,  while  the  meridian  of  greatest  curvature  would 
correspond  with  the  axis  of  the  minus  cylinder  (3  D)  if 
it  were  used. 

By  either  means  it  can  be  easily  proved  that  in  astig- 
matism of  any  kind  (myopic,  hyperopic,  or  mixed),  whose 
meridians  of  greatest  curvature  diverge  above,  there  is  a 
necessity  for  action  on  the  part  of  the  superior  oblique 
muscles  in  order  to  prevent  diplopia.  This  action,  hav- 
ing its  beginning  in  the  earliest  days  of  infancy  and  con- 
tinuing during  waking  hours  until  the  cause  is  corrected 
or  one  eye  is  lost,  converges  the  naturally  vertical  axes 
above.  If  the  meridians  of  greatest  curvature  converge 
above,  the  images  of  all  objects  are  so  displaced  in  the 
two  eyes  as  to  throw  into  activity  the  inferior  obliques, 
so  that  diplopia  may  be  prevented. 

In  astigmatism  with  the  principal  meridians  vertical 
and  horizontal,  the  only  eye  muscles  brought  into  ac- 
tion to  remedy,  in  any  way,  the  condition,  are  the  ciliary 
muscles.  In  oblique  astigmatism  with  the  meridians  of 
greatest  curvature  diverging  above,  there  is  the  same 
state  of  ciliary  strain  to  sharpen  as  much  as  possible  the 
images,  and  there  is  also  a  necessary  activity  of  the  su- 
perior obliques  so  as  to  bring  corresponding  parts  of  the 
two  retinas  under  the  oblique  images,  that  there  may  be 
binocular  single  vision.  Again,  in  oblique  astigmatism 
with  the  meridians  of  greatest  curvature  converging 


COMPENSATING    CYCLOTROPIA  461 

above,  there  is  the  ciliary  strain  for  sharpening  the 
images,  and  there  is  also  a  consequent  activity  of  the 
inferior  obliques  so  as  to  bring  similar  parts  of  the 
retinas  under  the  dissimilar  images,  resulting  in  binoc- 
ular single  vision. 

When  there  is  equality  of  strength  of  the  obliques  of 
the  two  eyes,  vertical  and  horizontal  astigmatism  will 
give  less  trouble  than  when  the  astigmatism  is  oblique 
in  either  direction,  and  astigmatism  with  the  meridians 
of  greatest  curvature  diverging  above  need  give  no  more 
annoyance  to  the  patient  than  if  these  meridians  con- 
verged above;  for,  in  the  former  case,  the  superior  ob- 
liques would  be  as  able  to  bear  the  strain  as  would  the 
inferior  obliques  in  the  latter  condition. 

But  the  obliques  are  not  always  harmonious :  the 
superior  obliques  are  insufficient  in  at  least  twenty-five 
per  cent  of  all  cases,  while  the  inferior  obliques  are  in- 
sufficient in  less  than  one  per  cent  of  all  cases.  In 
cases  of  insufficiency  of  the  superior  obliques,  the  ver- 
tical form  of  astigmatism  would  be  worse  on  the  patient 
than  if  he  had  oblique  astigmatism  with  the  meridians 
of  greatest  curvature  converging  above;  and  the  worst 
form  of  astigmatism  would  be  that  in  which  the  merid- 
ians of  greatest  curvature  diverge  above.  The  reverse 
would  be  true  if  the  inferior,  obliques  were  insufficient — • 
a  rare  condition. 


462  COMPENSATING   CYCLOTROPIA. 

The  complicated  function  of  the  oblique  muscles  exists 
only  in  cases  of  oblique  astigmatism  with  the  meridians 
of  greatest  curvature  converging  or  diverging-  above,  and 
in  unequal  degrees  of  oblique  astigmatism  when  the 
meridians  of  greatest  curvature  are  parallel.  The  ne- 
cessity for  this  function  is  entirely  destroyed  when  the 
astigmatism  is  properly  corrected;  but  the  action  of  the 
obliques  does  not  always  cease  at  once  in  binocular  single 
vision  through  the  correcting  cylinders.  The  old  habit 
of  rotation  often  continues  for  hours,  and  sometimes  for 
days  (although  there  is  no  longer  a  need  for  it),  and  the 
result  is  metamorphopsia.  Inherent  weakness  of  the 
superior  oblique  muscles,  in  a  large  per  cent  of  the 
cases,  leads  to  a  more  speedy  disappearance  of  the  met- 
amorphopsia when  the  meridians  of  greatest  curvature 
diverge  above  than  when  they  converge.  The  reverse 
would  be  true  in  a  case  of  insufficiency  of  the  inferior 
obliques.  The  habit  of  action  is  more  quickly  suspended 
in  a  weak  muscle  than  in  a  strong  one.  In  all  cases, 
however,  it  ceases,  and  the  metamorphopsia  vanishes, 
under  the  continuous  wearing  of  the  correcting  cylinders. 

A  careful  study  of  what  precedes  in  this  chapter  will 
show  that,  while  the  superior  obliques  must  fuse  the 
displaced  images  of  a  horizontal  line,  in  cases  of  astig- 
matism with  the  meridians  of  greatest  curvature  diverg- 
ing above,  the  inferior  obliques  must  fuse  the  displaced 


COMPENSATING  CYCLOTROPIA.          463 

images  of  a  vertical  line,  in  the  same  kind  of  cases. 
When  the  meridians  of  greatest  curvature  converge 
above,  the  displaced  images  of  a  horizontal  line  must 
be  fused  by  the  inferior  obliques,  while  the  displaced 
images  of  a  vertical  line  would  be  fused  by  action  of  the 
superior  obliques.  In  most  cases  of  oblique  astigmatism 
the  inferior  obliques  can  fuse  images  more  easily  than 
the  superior  obliques,  for  the  reason  that  the  former  are 
usually  stronger  than  the  latter;  but  when  a  figure  con- 
sists of  both  vertical  and  horizontal  lines,  such  as  a 
rectangle,  the  upper  and  lower  borders,  respectively,  of 
the  images  must  be  fused,  whether  by  the  inferior  obliques 
or  the  superior  obliques.  The  lateral  borders — the  verti- 
cal ends  of  the  rectangle — become  divergent  above  if  the 
fusion  has  been  effected  by  the  superior  obliques,  while 
they  become  divergent  below  if  the  fusion  has  been  ef- 
fected by  the  inferior  obliques.  There  is  no  known  rea- 
son for  the  fusion  of  the  upper  and  lower  borders  of 
images  to  the  detriment  of  the  lateral  borders,  and  it 
may  remain  always  an  unexplainable  fact. 

The  extent  of  displacement  of  images  of  horizontal 
lines  by  oblique  astigmatism  can  be  measured  only  b} 
the  cyclo-phorometer,  but  this  measurement  cannot  be 
accurately  made  if  there  is  a  complicating  cyclophoria. 
If  the  meridians  of  greatest  curvature  diverge  above  and 
there  is  a  complicating  plus  cyclophoria,  the  measure- 


464  COMPENSATING    CYCIXXTROPIA. 

ment  will  show  greater  displacement  than  really  exists; 
while  the  measurement  will  show  less  than  the  real  dis- 
placement when  the  meridians  of  greatest  curvature  con- 
verge above  and  there  is  a  complicating  plus  cyclophoria. 
In  measuring  the  displacement  of  the  image  by  oblique 
astigmatism,  the  single  Maddox  rod  must  be  used,  in  the 
cyclophrometer,  and  the  vertical  displacing  prism  must 
be  behind  one  rod  so  as  to  make  one  streak  of  lisrht  be- 

O 

low  the  other.  The  axis  of  each  rod  should  be  vertical. 
Both  eyes  having  oblique  astigmatism,  the  meridians  of 
greatest  curvature  diverging  above,  each  streak  of  light 
will  dip  toward  the  opposite  side.  Revolving  one  rod 
until  the  two  streaks  are  parallel,  though  not  horizontal, 
shows  the  sum  of  the  displacement  of  the  two  images; 
while  revolving  each  rod  until  the  two  streaks  are  hori- 
zontal, therefore  parallel,  the  extent  of  displacement  of 
the  image  in  each  eye  is  easily  read  on  the  scale.  This 
shows,  also,  the  amount  of  minus  cyclotropia  necessary 
for  the  fusion  of  the  two  images  of  a  horizontal  line. 
The  degree  of  displacement  of  the  image  of  a  horizontal 
line  depends  on  both  the  quantity  of  the  astigmatism 
and  the  extent  of  the  obliquity  of  the  meridian  of  great- 
est curvature  up  to  45°  from  the  vertical,  at  which  point 
there  is  the  maximum  of  displacement.  The  compensat- 
ing cyclotropia  of  the  two  eyes  always  equals  the  sum  of 
the  displacements  of  the  two  images. 


COMPENSATING    CYCLOTROPIA.  465 

The  apparent  dipping  of  the  streak  of  light  due  to 
cyclophoria  may  be  differentiated  from  that  caused  by 
oblique  astigmatism  by  substituting  the  triple  rod  for 
the  simple  rod.  With  the  triple  rod  the  dipping  line  of 
cyclophoria  will  be  unbroken,  while  the  dipping  line  of 
oblique  astigmatism  will  be  broken  into  as  many  parts 
as  there  are  rods,  the  one  part  slightly  over-riding  the 
other  in  the  direction  of  the  obliquity  of  the  most- 
curved  meridian. 

This  obliquity  of  the  image  varies  from  a  few  minutes 
to  a  few  degrees,  but  is  always  enough,  even  in  slight 
cases  of  oblique  astigmatism,  to  force  the  obliques  to 
disturb  the  parallelism  of  the  vertical  axes  with  the 
median  plane  of  the  head.  Persons  with  oblique  astig- 
matism, with  the  meridians  of  greatest  curvature  con- 
verging or  diverging  above,  cannot  have  correct  ideas  of 
direction,  except  in  line  of  the  visual  axes,  nor  can  they 
judge  correctly  of  verticality,  horizontality,  and  goni- 
ometry. 

The  abnormal  work  required  of  the  obliques  because 
of  oblique  astigmatism  (non-parallel)  develops  symptoms 
not  unlike  those  caused  by  cyclophoria. 

TREATMENT. 

The  treatment  of  compensating  cyclotropia  is  always 
non-surgical.  The  careful  correction  of  the  astigmatism 


466  COMPENSATING   CYCLOTROPIA. 

will  counteract  the  distortion  of  the  retinal  images  and 
relieve  the  cyclotropia,  but  not  at  once;  the  lifetime 
habit  of  the  obliques  cannot  be  broken  at  once;  but 
sooner  or  later  these  muscles  will  learn  that,  under  the 
new  condition  (the  wearing  of  the  correcting  cylinders), 
they  must  parallel  the  vertical  axes  of  the  eyes  with  the 
median  plane  of  the  head,  in  order  to  satisfy  the  law  of 
corresponding  retinal  points. 

In  all  cases  of  astigmatism,  one  eye  looking  through 
its  correcting  cylinder  will  see  at  once  a  rectangle  as 
a  rectangle;  and  if  the  meridians  of  greatest  curvature 
are  parallel — whether  vertical,  horizontal,  or  oblique' — the 
two  eyes  looking  through  the  cylinders  will  show  no  dis- 
tortion of  a  rectangular  figure.  The  reason  for  this  is 
that,  in  such  cases,  the  obliques  have  never  done  other 
work  than  the  keeping  of  the  vertical  axes  of  the  eyes 
parallel  with  the  median  plane  of  the  head;  therefore 
they  have  no  habit  to  break  when  cylinders  are  given. 
In  such  cases  the  glasses  are  worn  with  gladness  from 
the  beginning. 

There  is  always  metamorphopsia  to  annoy  a  patient 
whose  astigmatism  was  such  that  the  meridians  of 
greatest  curvature  diverged  above,  when  she  begins  the 
wearing  of  correcting  cylinders,  whether  they  be  plus 
or  minus.  This  distortion  is  easily  noticed,  for  it  is  the 
opposite  of  that  to  which  she  has  always  been  accustomed 


COMPENSATING    CYCLOTROPIA.  467 

and  which  she  may  never  have  noticed.  Seen  through 
the  correcting1  cylinders,  a  rectangle  will  appear  as  a 
a  trapezoid,  with  the  longer  side  below;  a  level  surface 
will  slant  toward  her;  and  a  vertical  object  will  lean 
toward  her.  The  metamorphopsia  is  due  to  the  fact 
that  the  superior  obliques,  always  in  the  habit  of  con- 
verging the  vertical  axes  of  the  eyes  in  binocular  vision, 
continue  to  thus  converge  them  for  a  time,  so  that  the 
axis  of  the  plus  cylinder  and  the  meridian  of  greatest 
curvature  do  not  remain  in  the  same  plane.  The  supe- 
rior obliques,  possibly  because  they  are  usually  weaker 
than  the  inferior  obliques,  readily  break  from  tljeir  old 
habit,  and  the  metamorphopsia  vanishes.  In  such  cases 
it  is  a  question  of  only  a  few  hours — or,  at  most,  a  few 
days — until  the  correcting  cylinders  can  be  worn  without 
annoyance  of  any  kind.  The  old  habit  broken,  the  me- 
ridian of  greatest  curvature  (least  if  a  minus  cylinder  is 
used)  and  the  axis  of  the  cylinder  lie  in  the  same  plane 
in  binocular  as  well  as  in  monocular  vision. 

When  the  meridians  of  greatest  curvature  converge 
above,  the  wearing  of  the  cylinders  will  be  attended  by 
metamorphopsia  for  a  much  longer  time,  possibly  be- 
cause the  inferior  obliques,  being  stronger  than  the  su- 
perior obliques,  are  less  inclined  to  give  up  the  old  habit 
of  diverging  the  vertical  axes  of  the  eyes,  in  the  act 
of  binocular  vision.  With  either  eye  alone,  a  rectangle, 


468  COMPENSATING   CYCLOTROPIA. 

seen  through  the  correcting-  cylinder,  will  be  a  rectangle; 
the  floor  will  appear  level,  and  a  vertical  object  will  not 
be  inclined.  In  binocular  vision  througfh  the  cylinders  a 
rectangle  will  appear  as  a  trapezoid,  with  its  longer  side 
above;  a  level  surface  will  slant  from  the  patient;  and  a 
vertical  object  will  lean  from  her.  These  appearances, 
being"  new,  will  be  easily  noticed,  and  will  often  prove 
very  annoying*  to  the  patient,  unless  previously  told 
about  them.  Finally,  the  old  habit  of  rotation  will 
cease,  and  the  metamorphopsia  will  disappear,  but 
only  after  days  or  weeks  of  constant  wearing  of  the 
cylinders. 

After  the  disappearance  of  the  metamorphopsia,  caused 
by  plus  cylinders,  whose  axes  diverge  above,  on  raising 
the  lenses  a  rectangle  will  appear  as  a  trapezoid,  with 
the  longer  side  above;  but  if  the  axes  of  the  cylinders 
converge  above,  on  raising  the  lenses  a  rectangle  will 
appear  as  a  trapezoid,  with  the  longer  side  below.  The 
same  changes  in  the  rectangle  existed  before  the  cyl- 
inders were  ever  prescribed,  but  they  were  unnoticed. 
Now  that  the  cylinders  have  corrected  the  misshaped 
images,  giving  perfect  vision,  on  raising  the  lenses  the 
misshaped  images  at  once  make  the  patient  conscious  of 
the  distortion  of  the  object. 

There  are  two  methods  of  dealing  with  cases  of  non- 
parallel  oblique  astigmatism  so  as  to  shorten  the  annoy- 


COMPENSATING  CYCLOTROPIA.          469 

ing-  period  of  habit-breaking  on  the  part  of  the  oblique 
muscles.  One  method  was  suggested  by  Lippincott, 
of  Pittsburg,  Pa.  He  advises  that  the  full  error  be 
determined  under  a  mydriatic,  and  that  the  exact  lo- 
cation of  the  principal  meridians  be  found,  which  can 
be  easily  done,  if  the  compensating  cyclotropia  is  not 
complicated  by  a  cyclophoria,  by  excluding  one  eye  whil« 
testing  the  other;  for  then  the  one  eye  assumes  that  po- 
sition which  makes  its  vertical  axis  parallel  with  the 
median  plane  of  the  head.  The  findings,  both  as  to 
strength  of  cylinders  and  positions  of  axes,  are  to  be 
recorded.  At  first  the  cylinders  given  should  be  one- 
third  the  full  strength  required,  but  their  axes  must  be 
placed  according  to  the  record.  When  the  little  meta- 
morphopsia  caused  by  the  partial  correction  has  disap- 
peared, new  cylinders  of  two-thirds  the  required  strength 
are  given.  The  little  metamorphopsia  caused  by  these, 
having  vanished,  the  full  correction  is  given.  These 
cause  but  slight  metamorphopsia,  and  that  for  only  a 
short  while. 

This  method  is  more  necessary  and  more  helpful  when 
the  meridians  of  greatest  curvature  converge  above,  and 
consequently  when  the  inferior  obliques  are  the  muscles 
involved.  A  full  correction  of  the  astigmatism  at  once 
corrects  the  shape  of  the  images,  so  as  to  make  them 
correspond  with  the  object.  These  images  would  now 


470  COMPENSATING    CYCLOTROPIA. 

fall  on  corresponding1  retinal  points  if  the  vertical  axes 
of  the  eyes  were  made  parallel  with  the  median  plane  of 
the  head.  To  thus  relate  the  vertical  axes,  the  inferior 
obliques  must  cease  their  efforts  to  diverge  them,  and  the 
superior  obliques  must  assume  the  labor  of  paralleling 
them.  Work  must  be  transferred  from  the  inferior  ob- 
liques (usually  stronger)  to  the  superior  obliques  (usu- 
ally weaker).  The  whole  load  cannot  be  shifted  at  once; 
and  as  long  as  the  inferior  obliques  continue  to  diverge 
the  vertical  axes,  so  long  will  the  metamorphopsia  re- 
main. Righting  the  images  one-third  transfers  one-third 
of  the  work  from  the  inferior  obliques  to  the  superior  ob- 
liques. This  small  load  is  kindly  and  quickly  accepted 
by  the  superior  obliques.  The  next  step  rights  the 
images  two-thirds,  and  transfers  another  one-third  of 
the  work  from  the  inferior  obliques  to  the  superior  ob- 
liques. Having  become  accustomed  to  the  first  trans- 
ference, the  superior  obliques  kindly  take  on  the  newly 
added  load.  The  next  step  fully  corrects  the  misshaped 
images,  and  transfers  the  balance  of  the  abnormal  work 
from  the  inferior  obliques,  in  the  shape  of  normal  work 
to  the  superior  obliques.  Having  already  become  accus- 
tomed to  doing  two-thirds  of  the  work  necessary  for 
paralleling  the  vertical  axes  of  the  eyes,  the  superior  ob- 
liques readily  assume  the  remaining  one-third  of  the  load 
that  they  must  now  carry.  For  this  class  of  astigmatics 


COMPENSATING    CYCLOTROPIA.  471 

the  Lippincott  plan  is  a  good  one.  The  only  objection 
to  the  method  is  the  cost  of  changing"  the  lenses. 

There  is  nothing1  to  contraindicate  the  giving  of  the 
full  correction,  at  once,  of  astigmatism  in  which  the 
meridians  of  greatest  curvature  are  parallel,  whether 
vertical,  horizontal,  or  oblique;  for,  in  these  cases,  the 
oblique  muscles  have  done  the  same  work  without  the 
correcting  cylinders  that  they  must  do  when  these  are 
given. 

In  only  high  degrees  of  oblique  astigmatism,  with  the 
meridians  of  greatest  curvature  diverging  above,  will  it 
be  necessary  to  adopt  the  Lippincott  plan;  for,  as  a 
rule,  the  weak  superior  obliques  are  ready  enough  to 
cease  doing  the  work  of  converging  the  vertical  axes 
of  the  eyes,  \vhile  the  inferior  obliques  just  as  readily 
assume  the  new  duty  of  paralleling  these  axes.  In  all 
cases,  as  soon  as  the  obliques  learn  to  parallel  the  verti- 
cal axes  of  the  eyes  with  the  median  plane  of  the  head, 
just  that  quickly  does  metamorphopsia  vanish. 

The  other  method  of  correcting  oblique  astigmatism  so 
that  there  shall  be  but  little  annoyance  from  metamor- 
phopsia is  to  give  at  once  the  cylinders  that  fully  correct 
the  errors,  and  to  have  each  lens  cut  so  that,  placed 
straight  in  the  frame,  its  axis  shall  be  in  a  plane  with 
the  meridian  of  greatest  curvature  (least  curvature  if 
the  lens  is  a  minus  cylinder)  when  the  vertical  axis  of 


472  COMPENSATING    CYCLOTROPIA. 

the  eye  is  parallel  with  the  median  plane  of  the  head. 
However,  these  lenses  must  not  be  placed  in  their  final 
positions  in  the  rims  at  first,  but  each  must  have  its  axis 
rotated  into  the  arc  of  distortion  for  the  obliques  that 
have  been  accustomed  to  doing  abnormal  work.  The 
rule  formulated  by  Dr.  N.  C.  Steele,  of  Chattanooga, 
Tenn.,  for  the  placing  of  the  axes  of  cylinders  in  oblique 
astigmatism,  is  a  good  one  to  follow  temporarily  under 
certain  conditions.  His  rule,  as  applied  to  plus  cylinders, 
is  as  follows: 

"  In  those  cases  in  which  the  axes  of  the  proper  con- 
vex cylinders  for  the  two  eyes  diverge,  place  the  cylin- 
ders in  those  positions  which  will  give  the  axes  the  great- 
est divergence  permitted  by  the  tests;  and  in  those  cases 
in  which  the  axes  converge,  place  them  at  the  points 
which  will  give  them  the  greatest  convergence  permitted 
by  the  tests." 

The  Steele  rule  for  placing  the  axes  of  plus  cylinders 
is  applicable  only  when  these  axes  are  \vithin  45°  of  the 
vertical.  Above  the  45°  point  the  shifting  of  these  axes 
should  be  from  the  vertical;  below  the  45°  point  the 
shifting  should  be  from  the  horizontal.  In  every  case 
of  oblique  astigmatism  with  the  meridians  of  greatest 
curvature  diverging  or  converging  above,  the  axes  of 
plus  cylinders  should  be  displaced  toward  the  center  of 
the  quadrants  in  which  they  are  found,  and  the  axes  of 


COMPENSATING    CYCLOTROPIA.  473 

minus  cylinders  should  be  shifted  from  the  center  of  the 
quadrants  in  which  they  are  found. 

The  shifting  should  be  only  enough  to  counteract  the 
metamorphopsia,  and  should  be  the  same  for  the  two 
cylinders.  Every  two  or  three  days  these  axes  should 
be  turned  a  degree  or  two  toward  the  location  determined 
in  the  monocular  test.  With  each  turning  the  meta- 
morphopsia will  be  so  little  as  hardly  to  be  noticed;  and 
finally,  when  the  cylinders  are  properly  located,  there  is  no 
metamorphopsia.  As  the  result  of  each  backward  turn- 
ing of  the  axes  of  the  cylinders,  the  obliques  more  nearly 
parallel  the  vertical  axes  of  the  eyes;  and  when  the  last 
turn  has  been  made,  the  vertical  axes  of  the  eyes  stand 
parallel  with  the  median  plane  of  the  head. 

As  the  Lippincott  method  is  specially  applicable  to 
those  cases  of  astigmatism  in  which  the  meridians  of 
greatest  curvature  converge  above,  so  is  it  with  the  ro- 
tation method.  When  the  meridians  of  greatest  curva- 
ture diverge  above — whether  the  astigmatism  be  hyper- 
opic,  myopic,  or  mixed,  unless  high  in  degree — the  full 
correction  should  be  given  at  once,  and  the  axes  should 
be  placed  in  the  positions  determined  by  the  monocular 
tests. 

If  the  Lippincott  method  be  resorted  to,  full  acuity  of 
vision  is  not  obtained  until  the  full  correction  of  the 
astigmatism  has  been  given;  in  the  method  of  rotating 


474  COMPENSATING   CYCLOTROPIA. 

the  full-strength  cylinders,  vision  is  more  or  less  blurred 
until  the  axes  are  placed  at  last  in  their  final  positions. 
As  to  acuteness  of  vision,  the  one  method  has  no  advan- 
tage over  the  other,  and  there  is  just  as  little  annoying 
metamorphopsia  in  the  one  method  as  in  the  other. 

It  is  almost  universally  true  that  astigmatics  whose 
meridians  of  greatest  curvature  diverge  above,  become 
speedily  accustomed  to  the  correcting  cylinders,  for  the 
reason  that  insufficiency  of  the  inferior  obliques  is  so 
rare — probably  not  found  in  more  than  one  case  in  two 
hundred.  There  are  some  astigmatics  whose  meridians 
of  greatest  curvature  converge  above,  who  can  never 
wear  comfortably  the  correcting  cylinders  because  of 
insufficiency  of  the  superior  obliques,  which  exists  in 
about  twenty-five  per  cent  of  all  cases. 

There  are  three  reasons  why  the  arcs  of  distortion,  by 
cylinders,  for  the  oblique  muscles,  should  be  studied:  (1) 
That  the  operator  may  know  how  to  place  cylinders  that 
they  may  give  rest  to  the  weaker  obliques  in  cyclopho- 
ria;  (2)  that  he  may  know  how  to  shift  the  cylinders  for 
oblique  astigmatics  so  as  to  lessen  the  annoyance  from 
metamorphopsia;  (3)  that  he  may  appreciate  the  impor- 
tance of  having  the  frames,  containing  the  cylinders  that 
correct  any  kind  of  astigmatism,  so  shaped  as  to  set 
perfectly  straight  before  the  eyes. 

Several  curious  facts  may  be  brought  forward  here, 


RIGHT 


UFT 


V  Fij.  * 

PLATE  IV 


(475) 


476  COMPENSATING   CYCLOTROPIA. 

and  reasons  have  been  given  why  advantage  should  be 
temporarily  taken  of  these  facts  in  certain  cases.  Fig1. 
1,  in  Plate  IV.,  represents  a  pair  of  hyperopic  astig- 
matic eyes,  the  meridians  of  greatest  curvature  being 
vertical  in  each  eye.  The  plus  cylinders — axes,  90°  (a) — 
insure  against  strain  of  either  the  superior  obliques  or  the 
inferior  obliques;  but  let  the  glasses  be  turned  in  their 
rims  so  that  the  axis  of  the  right  shall  stand  at  80°  (£) 
and  the  axis  of  the  left  at  100°  (&),  images  will  be  dis- 
torted, as  shown  in  Plate  II.,  which  would  necessitate 
strain  on  the  part  of  the  superior  oblique  muscles.  The 
distortion  of  the  images  would  increase,  and  the  strain 
on  the  superior  obliques  would  be  greater,  as  the  axes 
are  revolved  farther  away  from  the  vertical,  the  maxi- 
mum being  reached  at  45°  (c)  for  the  right  eye  and  135° 
(c)  for  the  left  eye.  Passing  these  points,  the  distor- 
tion grows  less,  until  at  180°  (d~)  for  each  eye.  it  disap- 
pears. 

Fig.  2  represents  the  same  pair  of  eyes.  If  now  the 
axis  of  the  right  cylinder  should  be  revolved  from  90°  (a) 
to  100°  (£)  and  that  of  the  left  cylinder  from  90°  («)  to  80° 
(£),  the  distortion  of  images  \vould  be  such  as  to  call  into 
activity  the  inferior  obliques,  so  that  there  might  be 
binocular  single  vision.  This  distortion  would  reach  its 
maximum  when  the  axis  of  the  right  cylinder  stands  at 
135°  (c)  and  that  of  the  left  cylinder  at  45°  (c),  again  les- 


COMPENSATING    CYCLOTROPIA.  477 

sening  as  the  axes  are  made  to  approach  the  horizontal, 
where  the  distortion  ceases. 

Fig1.  3,  Plate  IV.,  represents  a  pair  of  hypermetropic 
astigmatic  eyes  with  the  meridian  of  greatest  curvature 
of  the  right  at  70°  (a)  and  that  of  the  left  at  110°  (a). 
(In  all  the  figures  of  Plate  IV.,  Plate  V.,  and  Plate  VI., 
the  mark  within  the  circle  shows  the  location  of  the 
meridian  of  greatest  curvature.)  These  meridians,  con- 
verging above,  would  cause  strain  of  the  inferior  ob- 
liques, which  -would  be  relieved  by  the  correcting  cylin- 
ders, axis  of  the  right  at  70°  (a)  and  of  the  left  at  110° 
(«).  A  revolution  of  the  axis  of  the  right  cylinder  to  45° 
(&)  and  that  of  the  left  cylinder  to  135°  (&)  would  so  dis- 
place the  images  as  to  call  into  action  the  superior  ob- 
liques, the  displacement  increasing  as  the  axes  are  moved 
until  these  points  (b  for  each  eye)  are  reached.  Continu- 
ing the  revolution  of  the  cylinders  in  the  same  directions, 
the  displacement  lessens,  and  disappears  entirely  when 
the  axis  of  the  right  reaches  20°  (c)  and  that  of  the  left 
reaches  160°  (c),  when  the  necessity  for  over-action  of  the 
obliques  no  longer  exists.  If  the  axes  of  the  cylinders  are 
moved  from  their  correct  positions  (70°  for  the  right  eye 
and  110°  for  the  left  eye)  tp  90°  (/)  for  each  eye,  images 
will  be  so  displaced  as  to  call  into  compensating  activity 
the  inferior  obliques.  The  maximum  of  displacement 
would  be  effected  when  the  axis  reaches  135°  (e)  in  the  right 


478  COMPENSATING   CYCLOTROPIA. 

eye  and  45°  (e]  in  the  left  eye.  Continuing'  the  revolution 
in  the  same  directions,  the  displacement  would  grow  less, 
and  finally  disappear  when  the  axis  of  the  right  eye  stands 
at  d,  and  that  of  the  left  eye  at  d,  each  20°  above  the  hori- 
zontal. As  will  be  seen,  the  arc  of  distortion,  so  as  to 
throw  strain  on  the  superior  obliques,  is  50°  (from  70°  to 
20°  in  the  right  eye  and  from  110°  to  160°  in  the  left  eye), 
while  the  arc  of  distortion  that  would  throw  strain  on  the 
inferior  obliques  is  130°  (from  a  to  d}. 

Fig1.  4,  Plate  IV.,  shows  the  meridians  of  greatest 
curvature  of  these  hypermetropic  astigmatic  eyes  at 
110°  («)  for  the  right  and  70°  («)  for  the  left.  These  me- 
ridians, diverging  above,  would  call  into  compensating 
activity  the  superior  oblique  muscles.  Correctly  chosen 
and  properly  placed  cylinders,  by  correcting  the  distor- 
tion of  the  images,  would  remove  the  necessity  for  the 
performance  of  the  complicated  function  of  the  superior 
obliques.  Displacing  the  axes  of  these  cylinders,  the 
right  to  135°  (&)  and  the  left  to  45°  (&),  would  cause  a 
maximum  of  distortion  of  the  images,  of  the  kind  to  call 
into  action  the  inferior  obliques.  Continuing  the  revo- 
lution of  the  cylinders,  the  distortion  would  disappear 
when  the  axis  of  the  right  reaches  160°  (c)  and  that  of 
the  left  reaches  20°  (c).  Should  the  axes  of  the  cylinders 
be  revolved  from  their  proper  places — at  110°  (a)  in  the 
right  and  70°  (a)  in  the  left— to  90°  (/)  for  each  eye,  the 


COMPENSATING  CYCLOTROPlA.          479 

images  would  be  so  changed  as  to  call  into  harmonious 
activity  the  superior  obliques.  The  maximum  distortion 
would  occur  when  the  axis  of  the  right  is  at  45°  (<?)  and 
that  of  the  left  at  135°  (e).  Continuing  the  revolution, 
the  distortion  would  disappear  when  the  axes  reach  the 
points  d  above  the  horizontal  meridians.  In  this  case 
the  arc  of  distortion  causing  activity  of  the  inferior  ob- 
liques is  50°  (from  a  to  c),  while  the  arc  of  distortion  that 
would  throw  strain  on  the  superior  obliques  is  130°  (from 
a  to  d).  If  in  this  pair  of  eyes  the  meridians  of  greatest 
curvature  had  been  at  130°  for  the  right  and  50°  for  the 
left,  the  arc  of  distortion  that  would  call  the  inferior  ob- 
liques into  action  would  be  only  10°,  while  the  one  that 
would  cause  activity  of  the  superior  obliques  would  be 
170°  (180°  less  10°). 

Fig.  1,  Plate  V.,  represents  hypermetropic  astigmatic 
eyes,  the  meridians  of  greatest  curvature  being  at  180° 
(a)  in  each  eye — a  condition  that,  in  itself,  would  not  call 
either  the  superior  obliques  or  the  inferior  obliques  into 
activity.  The  correct  plus  cylinders — axes,  180°— would 
sharpen  the  blurred,  but  not  distorted,  images.  Displa- 
cing these  axes  in  the  lower  temporal  quadrants  would  so 
distort  the  images  as  to  throw  into  action  the  superior 
obliques;  and  the  maximum  of  distortion  would  be  effected 
when  the  axes  reached  45°  (c)  in  the  right  e}re  and  135°  (c) 
in  the  left  eye.  With  the  axes  turned  to  90°  (</),  there 


(ISO) 


FIJ  + 

PLATE  V. 


COMPENSATING   CYCLOTROPIA.  483 

would  be  no  distortion  of  images,  though  there  would  be 
blurring-,  as  in  all  cases  of  displaced  cylinders. 

Fig.  2,  Plate  V.,  represents  the  same  pair  of  eyes 
shown  in  Fig.  1.  Revolving  the  axes  of  the  correcting 
cylinders  in  the  lower  nasal  quadrant,  would  so  distort 
images  as  to  call  into  action  the  inferior  oblique  muscles, 
the  maximum  being  effected  when  the  axes  stand  at  135° 
(c)  for  the  right  eye  and  45°  (c)  for  the  left  eye,  the  distor- 
tion lessening  as  the  axes  approach,  and  disappearing 
altogether  when  they  reach,  90°  (d'). 

A  comparative  study  of  Fig.  1  and  Fig.  2  of  Plate  IV., 
with  Fig.  1  and  Fig.  2  of  Plate  V.,  will  show  that,  in 
hypermetropic  astigmatism  with  the  meridians  of  great- 
est curvature  either  vertical  or  horizontal,  a  revolution 
of  the  axes  of  the  cylinders  in  the  lower  temporal  quad- 
rant will  distort  images  (as  of  a  rectangle)  down  and  in, 
and  will  thus  call  into  harmonious  action  the  superior 
obliques;  and  it  will  also  show  that  a  revolution  of  the 
cylinders  in  the  lower  nasal  quadrants  will  so  displace 
the  images  as  to  call  into  harmonious  action  the  inferior 
obliques. 

Fig.  3,  Plate  V.,  represents  a  pair  of  hypermetropic 
astigmatic  eyes  with  the  meridian  of  greatest  curvature 
for  the  right  eye  at  20°  (a)  and  that  of  the  left  eye  at  160° 
(a).  Since  these  meridians  converge  above,  the  uncor- 
rected  condition  would  cause  harmonious  action  of  the 


482  COMPENSATING   CYCLOTROPIA. 

inferior  obliques.  Properly  chosen  and  correctly  placed 
cylinders,  axes  at  20°  (a)  for  the  right  eye  and  160°  («)  for 
the  left  eye,  would  relieve  the  distortion  of  the  images 
and  do  away  with  the  necessity  for  the  compensating  ac- 
tion of  the  obliques.  Revolving  the  axis  of  the  right  cyl- 
inder from  20°  («)  to  45°  (£)  and  that  of  the  left  cylinder 
from  160°  (a)  to  135°  (£)  would  cause  a  maximum  displace- 
ment of  images  in  such  a  way  as  to  call  into  action  the 
superior  oblique  muscles,  the  distortion  disappearing 
when  these  axes  reach  70°  (e)  for  the  right  eye  and  110° 
(c)  for  the  left  eye.  Passing  70°  (c)  in  the  right  eye  and 
110°  (c)  in  the  left  eye,  the  distortion  becomes  reversed, 
so  that  the  strain  will  be  thrown  on  the  inferior  obliques, 
the  maximum  being  attained  when  the  axis  of  the  right 
stands  at  135°  (<?)  and  that  of  the  left  at  45°  (*).  The 
distortion  decreases  as  the  axes  are  still  farther  turned 
in  the  same  directions,  and  disappears  at  the  end  of  the 
arc  of  130°  (from  c  to/")  when  they  coincide  with  the 
meridians  of  greatest  curvature.  Thus  the  arc  of  dis- 
tortion involving  the  superior  obliques  is  50°  ( from  a  to 
c\  while  that  involving  the  inferior  obliques  is  130° 
(from  ctof). 

The  eyes  ( hypermetropic  astigmatic)  represented  by 
Fig.  4,  Plate  V.,  have  their  meridians  of  greatest  cur- 
vature at  160°  («)  in  the"  right  and  20°  («)  in  the  left. 
These  meridians  diverging  above  would  result,  in  the 


COMPENSATING  CYCLOTROPIA.          483 

uncorrected  case,  in  calling-  into  harmonious  action  the 
superior  obliques.  Proper  cylinders  with  the  axis  of  the 
right  at  160°  (a)  and  that  of  the  left  at  20°  (a)  would  cor- 
rect the  distortion  of  the  images  and  relieve  the  strain 
on  the  superior  obliques.  A  turning  of  these  C}'linders 
in  the  arcs  a-c  would  distort  the  retinal  images  so  as  to 
bring1  into  action  the  inferior  oblique  muscles,  the  maxi- 
mum distortion  existing-  when  the  axes  are  at  b.  Con- 
tinuing- the  revolution  from  c,  the  distortion  becomes  re- 
versed, and,  as  a  consequence,  the  superior  obliques  are 
brought  into  activity,  the  maximum  being-  attained  when 
the  axes  reach  e.  As  the  axes  are  revolved  farther,  the 
distortion  lessens,  and  finally  disappears  when  they  stand 
at  f,  again  coinciding-  with -the  meridians  of  greatest 
curvature.  In  this  pair  of  eyes  the  arc  of  distortion  in- 
volving- the  inferior  obliques  is  50°  (from  a  to  c},  while 
that  involving  the  superior  obliques  is  130°,  the  maximum 
of  distortion  in  both  instances  being  attained  when  the 
halfway  point  of  the  arc  is  reached  by  the  axis  of  the 
cylinder. 

A  comparative  study  of  any  two,  or  all,  of  the  figures 
in  Plate  IV.  and  Plate  V.,  will  show  that  the  arc  of  dis- 
tortion, by  corrective  plus  cylinders,  involving  the  supe- 
rior obliques,  is  always  in  the  lower  temporal  quadrant, 
wholly  or  in  greater  part;  and  if  entirely  within  this 
quadrant,  its  length  is  always  t\vice  the  distance  from 


484  COMPENSATING    CYCLOTROPIA. 

the  meridian  of  greatest  curvature  to  the  45°  point  of  the 
quadrant,  the  other  half  being1  on  the  opposite  side  of 
the  latter.  In  like  manner  it  will  be  seen  that  the  arc 
of  distortion  involving'  the  inferior  obliques,  by  a  revo- 
lution of  plus  cylinders,  is  always  in  the  lower  nasal 
quadrant,  wholly  or  in  greater  part;  and  if  entirely 
within  the  quadrant,  its  length  is  twice  the  distance 
from  the  meridian  of  greatest  curvature  to  the  45°  point 
of  the  quadrant,  the  other  half  being1  on  the  opposite 
side  of  the  latter.  When  the  arc  of  distortion  involving 
the  superior  obliques  is  90°,  that  involving*  the  inferior 
obliques  is  90°,  and  vice  versa;  when  the  arc  of  distor- 
tion involving*  the  superior  obliques  is  less  than  90°,  the 
arc  involving*  the  inferior  obliques  is  always  the  differ- 
ence between  the  former  and  180°,  and  vice  versa.  The 
maximum  of  distortion  is  always  attained  when  the  axis 
of  the  cylinder  is  at  the  halfway  point  of  the  arc. 

Fig*.  1,  Plate  VI.,  represents  a  pair  of  hypermetropic 
astig*matic  eyes,  the  meridian  of  greatest  curvature  of 
the  right  eye  at  45°  (a]  and  that  of  the  left  eye  at  135°  (a). 
These  meridians  converging  above  would  cause  such  dis- 
tortion of  images  as  to  throw  into  harmonious  action  the 
inferior  oblique  muscles.  The  proper  cylinders,  correct- 
ly placed — the  axis  of  the  right  at  45°  (a)  and  the  axis 
of  the  left  at  135°  (a) — would  counteract  the  distortion 
and  relieve  the  inferior  obliques  of  the  necessity  of  over- 


COMPENSATING  CYCLOTROPIA. 


485 


acting.  Revolving-  the  axes  of  the  correcting1  cylinders 
in  either  direction  would  so  distort  images  as  to  call  into 
harmonious  action  the  inferior  oblique  muscles.  Since 
the  arc  of  distortion  for  the  superior  obliques  in  this 
case  is  nothing-,  the  arc  of  distortion  for  the  inferior 


R/GHT 


obliques  is  180°,  from  a  to  d  in  either  direction,  the 
maximum  of  distortion  being-  attained,  respectively,  at  e 
above  and  at  c  below. 

Fig-.  2,  Plate  VI.,  represents  a  pair  of  the  same  kind  of 
eyes,  but  with  the  meridian  of  greatest  curvature  at  135° 
(a)  for  the  right  eye  and  45°  (a)  for  the  left  eye.  These 


486  COMPENSATING   CYCLOTROPIA. 

meridians  diverging-  above,  the  refraction  is  such  as  to 
distort  images  so  as  to  call  into  harmonious  action  the 
superior  obliques.  As  in  the  other  case,  the  correct  cyl- 
inders, properly  placed,  counteract  the  distortion  and  re- 
lieve the  superior  obliques  from  action.  Rotating  the 
axes  of  these  cylinders  in  either  direction  from  a  would 
so  distort  images  as  to  call  into  activity  the  superior  ob- 
liques. In  this  case  the  arc  of  distortion  for  the  inferior 
obliques  is  nothing,  and,  therefore,  the  arc  of  distortion 
for  the  superior  obliques  is  180°,  from  a  to  d  in  either 
direction,  the  maximum  being  attained  at  c  above  and  at 
e  below. 

In  the  adjustment  of  cylinders  for  the  correction  of 
astigmatism — whether  it  be  vertical,  horizontal,  or  ob- 
lique— a  knowledge  of  the  arcs  of  distortion  by  displaced 
cylinders  is  of  great  importance.  Patients  should  be 
impressed  with  the  absolute  necessity  of  keeping  the 
rims  containing  the  glasses  in  such  relationship  to  each 
other  that  a  straight  edge  would  pass  through  the  fol- 
lowing four  points :  the  two  points  where  the  temple 
pieces  join  the  rims  and  the  two  points  of  attachment  of 
the  nose  bridge  to  the  rims.  If  the  frames  should  be  so 
bent  that  the  long  axis  of  each  lens  would  lean  down  and 
out,  and  the  astigmatism  is  according  to  the  rule,  the 
cylinders  would  be  displaced  in  the  arc  of  distortion  for 
the  inferior  obliques,  which,  usually,  would  be  borne 


COMPENSATING  CYCLOTROPIA.          487 

fairly  well;  but  when  the  astigmatism  is  against  the 
rule,  this  displacement  would  be  in  the  arc  of  distortion 
for  the  superior  obliques,  and  would  cause  much  annoy- 
ance. This  would  be  true,  whether  the  astigmatism 
were  hyperopic,  myopic,  or  mixed. 

If  the  frames  should  be  so  bent  that  the  long  axes  of 
the  lenses  pointed  down  and  in,  the  astigmatism  being 
according  to  the  rule,  the  axes  of  the  cylinders  would  be 
displaced  in  the  arcs  of  distortion  for  the  superior  ob- 
liques, and  would  cause  trouble;  but  if  the  astigmatism 
were  against  the  rule,  the  displaced  axes  \vould  be  in  the 
arcs  of  distortion  for  the  inferior  obliques,  and  but  little 
trouble  would  result  unless  the  displacement  should  be 
considerable. 

If  the  frames  are  so  shaped  that  the  long  axis  of  each 
lens  lies  in  the  same  plane  with  the  long  axis  of  the 
other,  the  leaning  of  the  common  plane  down  and  to  the 
right,  resulting  from  a  bend  upward  of  the  temple  piece 
on  the  corresponding  side,  or  a  bend  downward  of  the 
temple  piece  on  the  opposite  side,  the  cylinders  being 
of  equal  strength,  no  strain  of  the  obliques  will  be 
excited,  for  the  reason  that  the  distortion  in  the  one 
eye  would  be  similar  to  the  distortion  in  the  other. 
Vision  would  be  blurred  and  all  objects  would  appear 
out  of  their  proper  places.  The  ciliary  muscles  might 
make  an  attempt  to  sharpen  the  images,  but  there  would 


488         COMPENSATING  CYCLOTROPIA. 

be  no  necessity  for  the  obliques  to  make  an  effort  either 
to  diverge  or  converge  the  vertical  axes  of  the  eyes  in 
order  that  there  might  be  fusion  of  the  displaced  images. 
The  same  would  be  true  if  the  straight  frames  were 
made  to  incline  down  and  to  the  left.  Bent  frames  are 
capable  of  doing  more  or  less  harm  through  abnormal 
excitation  of  the  brain-centers  controlling  the  oblique 
muscles. 

Spectacle  frames  should  be  given  astigmatics,  for  the 
reason  that  they  can  be  much  better  adapted  to  the  face 
than  the  most  perfect-fitting  nose-glass  frames  that  have 
ever  been  invented. 

A  knowledge  of  the  character  of  distortion  of  retinal 
images,  by  oblique  corneal  astigmatism,  enables  the  op- 
erator to  tell  the  patient  beforehand  just  the  kind  of 
metamorphopsia  that  will  result  from  the  wearing  of 
the  correcting  cylinders,  and  whether  it  will  soon  van- 
ish or  be  a  long  time  in  disappearing. 

When  one  eye  is  set  lower  in  its  orbit  than  the  other, 
there  must  be  a  compensating  cyclotropia  in  the  direction 
of  the  lower  eye,  effected  by  either  the  8th  conjugate 
center  (left  eye,  the  lower)  or  the  9th  conjugate  center 
(right  eye,  the  lower).  For  this  there  is  no  relief.  If 
such  a  patient  should  be  astigmatic,  the  correcting 
cylinders,  whether  plus  or  minus,  should  both  be  rotated 
in  the  direction  of  the  lower  eye,  through  a  small  arc. 


CHAPTER   IX. 


COMPENSATING    LATERAL   AND   VERTICAL 
HETEROTROPIA. 


THE  recti  muscles  may  be  perfectly  developed,  their 
attachments  may  be  ideal,  and  their  innervation  centers 
may  be  faultless;  nevertheless,  if  there  is  any  form  of 
anisometropia,  there  must  be  some  form  of  heterotropia 
whenever  the  visual  lines  are  made  to  sweep  from  the 
primary  point  to  some  other  point  of  view.  If  the  right 
eye  is  emmetropic  and  the  left  eye  is  hyperopic,  the  im- 
age of  a  square  will  be  larger  in  the  former  than  in  the 
latter.  When  the  point  of  fixation  is  the  center  of  the 
square,  the  recti  will  have  the  visual  axes  in  the  same 
plane  and  will  cause  them  to  intersect  at  the  point  of 
view.  If  the  point  of  view  is  to  be  changed  from  the 
center  of  the  square  upward,  so  as  to  fuse  the  upper 
border,  it  becomes  evident  that  the  visual  axis  of  the 
right  eye  must  rise  higher  than  the  visual  axis  of  the 
left  eye.  Without  this  compensating  hypertropia  these 
borders  could  not  be  fused.  Again,  if  the  point  of  view 
is  to  be  changed  from  the  center  of  the  square  down- 

U89) 


490         COMPENSATING  LATERAL  AND 

ward,  so  as  to  fuse  the  lower  border,  the  visual  axis  of 
the  emmetropic  eye  must  travel  farther  than  that  of  the 
hyperopic  eye  in  order  to  fuse  the  lower  borders.  The 
cause  of  the  fusion  is  a  compensating-  catatropia  of  the 
emmetropic  e}re.  If  the  point  of  view  is  to  be  changed 
from  the  center  of  the  square  to  its  right  border,  the 
visual  axis  of  the  right  eye  must  sweep  farther  to  the 
right  than  that  of  the  left  eye,  or  the  borders  cannot  be 
fused.  This  is  accomplished  by  a  compensating  exotro- 
pia  of  the  right  eye.  Likewise  there  must  be  a  compen- 
sating esotropia  of  the  right  eye,  if  the  point  of  view 
must  be  changed  from  the  center  of  the  square  to  its  left 
border.  All  of  this  is  illustrated  by  Fig.  74,  taken  from 
Chapter  VIII.,  in  which  a-b-c-d  represents  the  square 
as  seen  by  the  hyperopic  eye,  and  a"-b"-c"-d"  repre- 
sents the  square  as  seen  by  the  emmetropic  eye.  The 
distance  from  e  to  the  line  a"-d"  is  greater  than  to  the 
line  a-d. 

The  same  figure  shows  that  if  one  eye  were  emme- 
tropic and  the  other  eye  were  myopic,  the  larger  square 
— a"-b"-c"-d" — would  be  seen  by  the  myopic  eye,  while 
the  smaller  square  (a-b-c-d}  would  be  seen  by  the  emme- 
tropic eye.  In  such  a  pair  of  eyes  the  compensating 
heterotropia  would  be  confined  to  the  myopic  eye. 

Again  referring  to  the  same  figure,  if  one  eye  had 
myopic  astigmatism,  the  meridian  of  greatest  curvature 


VERTICAL,   HETEROTROPIA. 


491 


vertical,  it  would  see  the  square  as  a'-b'-c'-d',  while  the 
other  eye,  being"  emmetropic,  would  see  the  square  as  it 
really  is — a-b-c-d.  In  such  eyes  there  would  be  no  com- 
pensating' lateral  heterotropia,  for  a-b  coincides  with 
a'-b'  and  d-c  coincides  with  d'-c' ;  but  there  will  be  ver- 


Fig-  74- 

tical  compensating1  heterotropia,  for  the  reason  that  e  is 
nearer  a-d  and  b-c  than  it  is  to  a'-d'  and  b'-c' . 

In  the  same  way  all  forms  of  anisometropia  may  be 
studied,  showing1  the  necessity  for  compensating  hetero- 
tropia on  the  part  of  the  eye  having-  the  greater  refract- 
ive power,  or  the  eye  that  is  long-er. 


492         COMPENSATING  LATERAL  AND 

As  compensating  cyclotropia  is  always  cured  by  the 
application  of  obliquely-placed  cylinders,  so  compensat- 
ing lateral  and  vertical  heterotropias  are  cured  by  the 
lenses  needed  for  the  correction  of  the  focal  errors.  It 
is  more  necessary  to  correct  unequal  refraction,  though 
the  errors  be  not  great,  than  it  is  to  correct  greater  er- 
rors that  are  equal  in  the  two  eyes. 

Prisms  and  lenses  rendered  prismatic  by  decentration 
cause  compensating  heterotropia  in  the  direction  of  the 
apex  of  the  prism;  therefore,  prisms  given  for  con- 
stant wearing  to  an  exophoric,  cause  compensating  exo- 
tropia;  prisms  given  to  an  esophoric  develop  a  compen- 
sating esotropia;  and  a  prism  placed  base  down  for  the 
relief  of  a  hyperphoria  generates  a  compensating  hyper- 
tropia  of  that  eye. 

In  spherical  anisometropia  the  law  of  direction  is  in- 
terfered with,  so  far  as  the  eye  of  greatest  refraction  is 
concerned,  except  when  the  two  eyes  are  in  the  primary 
position.  When  there  is  astigmatism  of  one  eye  and 
emmetropia,  hyperopia,  or  myopia  of  the  other,  there  can 
be  no  heterotropia  in  the  direction  of  that  principal  me- 
ridian of  the  astigmatic  eye  which  has  the  same  radius  of 
curvature  as  the  non-astigmatic  cornea  of  the  other  eye; 
but  in  the  direction  of  the  other  meridian  there  will  be 
compensating  heterotropia.  In  the  compensating  hetero- 
tropia caused  by  prisms  and  decentered  lenses  there  is 


VERTICAL    HETEROTROPIA.  493 

interference  with  the  law  of  direction  in  all  parts  of  the 
field  of  view. 

DECENTERED  CORNEAS  AND  MISPLACED  MACULAS. 
—There  are  two  other  causes  for  compensating-  vertical 
and  lateral  heterotropia.  The  one  is  a  decentration  of 
the  cornea;  the  other  is  displacement  of  the  macula.  It 
would  probably  be  more  nearly  correct  to  say  that  there 
is  but  one  other  cause — that  is,  decentration  of  the  cornea. 
The  antero-posterior  axis  of  the  eye,  that  axis  controlled 
by  the  recti  muscles,  which  must  always  be  at  right 
angles  to  the  equator  of  the  eye,  can  be  none  other  than 
the  visual  axis.  Commencing  always  at  the  fovea  cen- 
tralis,  it  passes  always  through  the  center  of  retinal 
curvature  and  thence  through  the  center  of  an  ideally 
placed  cornea;  but  if  the  cornea  is  not  properly  centered, 
the  visual  axis  passes  through  some  other  part  than  the 
center.  The  posterior  pole  of  the  eye,  whether  near  to 
or  far  away  from  the  optic  disc,  or  above  or  below  it,  is 
the  center  of  the  macula;  the  anterior  pole  may  or  may 
not  be  the  center  of  the  cornea.  In  ideal  eyes — eyes  that 
see  best  or  can  be  made  to  see  best — the  anterior  pole  is 
the  center  of  the  cornea.  The  antero-posterior  axis  of 
the  eye,  as  given  by  anatomists  and  adopted  by  writers  of 
books  on  the  eye,  has  its  beginning  at  the  center  of  the 
cornea,  passes  backward  through  the  center  of  rotation, 
and  strikes  the  retina,  maybe  at  the  macula,  but  is  just  as 


494  COMPENSATING   LATERAL    AND 

likely  to  strike  it  elsewhere.  The  error  is  in  giving  the 
anterior  pole  a  fixed  location — the  center  of  the  cornea. 
Such  an  axis  can  be  at  right  angles  to  the  equator  of  the 
eye  in  which  lie  the  vertical  and  transverse  axes  of  the 
eye,  only  when  it  coincides  with  the  visual  axis.  It  can 
be  of  value  only  in  determining  the  extent  of  the  decen- 
tration  of  the  cornea,  or  how  much  the  cornea  lacks  of 
occupying  the  ideal  position. 

In  true  compensating  heterotropia,  retinal  images  on 
the  maculas  are  either  sharp  or  can  be  made  so;  but 
when  there  is  decentration  of  the  corneas,  the  rays  of 
light  that  strike  the  maculas  are  never  perfectly  focused, 
nor  can  they  be  made  to  focus  perfectly  by  any  artificial 
means.  In  true  compensating  heterotropia,  that  caused 
by  anisometropia,  or  by  prisms,  there  is  interference 
with  the  law  of  direction.  This  is  not  true  of  decentra- 
tion of  the  cornea;  for  the  visual  axis  points  directly  to 
the  source  of  the  light,  although  the  eye  appears  to  be 
pointing  in  some  other  direction  as  indicated  by  the  posi- 
tion of  the  center  of  the  cornea.  The  heterotropia,  then, 
is  apparent,  and  not  real;  therefore  it  cannot  be  prop- 
erly called  a  "compensating  heterotropia."  The  angle 
gamma  measures  the  apparent  deviation  of  the  eye  and 
the  real  displacement  of  the  cornea. 

When  an  eye  whose  cornea  is  ideally  situated  is  ex- 
amined with  the  Javal  ophthalmometer,  the  reflected 


VERTICAL,    HETEROTROPIA.  495 

disc  will  have  its  center  coincide  with  the  center  of  the 
cornea;  but  if  the  cornea  is  displaced  out,  the  reflection 
will  be  more  from  the  nasal  side;  if  displaced  in,  the  re- 
flection will  be  in  greater  part  from  the  temporal  side; 
if  displaced  down,  the  greater  part  of  the  reflection  will 
be  from  the  upper  part  of  the  cornea;  and  if  displaced 
up,  the  reflected  image  will  be  more  below  than  above. 
Oblique  displacement  of  the  cornea  will  show  an  oblique 
displacement  of  tie  reflected  image  of  the  ophthalmom- 
eter  disc.  These  examinations,  to  be  accurate,  must  be 
made  while  the  patient  is  looking*  directly  into  the  center 
of  the  telescopic  tube,  and  the  reflected  image  must  be 
looked  at  through  the  center  of  the  leveling  slit  above 
the  telescope.  A  considerable  proportion  of  corneas  thus 
examined  will  show  slight  displacements,  but  rarely 
more  than  5°.  When  the  angle  gamma  is  much  in  ex- 
cess of  5°,  it  means  that  the  acuteness  of  vision  can- 
not be  made  equal  to  20-20. 

The  various  forms  of  heterophoria,  and  anyone  of  the 
true  heterotropias,  may  be  found  in  e}^es  whose  corneas 
are  not  properly  centered.  The  former  should  be  dealt 
with  in  the  manner  prescribed  in  the  chapters  preceding 
this  one;  and  the  true  heterotropias  should  be  treated 
after  the  methods  to  be  set  forth  in  the  next  chapter. 
For  apparent  heterotropia  nothing  can  be  done;  so,  there- 
fore, nothing  should  be  attempted.  In  operating  for  the 


496  COMPENSATING   HETEROTROPIA. 

relief  of  true  heterotropia,  it  should  be  known  whether 
or  not  there  is  a  false  heterotropia  as  well,  else  the  treat- 
ment might  result  disastrously. 

The  new-formed  physiologic  macula  that  some  think 
they  have  found  in  a  squinting  eye,  is  the  old  macula  of 
an  eye  whose  cornea  is  not  correctly  placed.  There  is 
no  part  of  one  eye,  save  the  macula,  that  can  harmonize 
with  the  macula  of  the  other.  Because  of  opacities  in 
the  refractive  media,  or  because  of  disease  of  the  cho- 
roid  behind  the  macula,  a  peripheral  part  of  the  retina 
of  that  eye  must  be  used,  but  it  can  never  be  made 
a  macula;  it  can  never  be  made  to  harmonize  with  the 
macula  of  the  healthy  fellow  eye. 


CHAPTER  X. 


HETEROTROPIA. 


THE  appearance  of  eyes  whose  muscles  fail  to  co- 
ordinate them,  rendering"  binocular  single  vision  impos- 
sible, has  been  designated  by  the  terms  "squint," 
"strabismus,"  and  "cross-eyes,"  by  both  ancient  and 
modern  writers.  It  may  be  long  before  these  terms  can 
be  entirely  eliminated,  although  there  is  now  no  good 
reason  for  retaining  them.  "  Heterotropia, "  a  term  in- 
troduced by  Stevens,  carries  its  own  meaning  with  it, 
the  plain  English  of  \vhich  is  a  "wrong  turning."  This 
term  should  be  preferred,  not  only  because  of  its  sim- 
plicity, but  also  because  it  is  in  conformity  with  the  now 
universally  accepted  term,  "heterophoria,"  as  applied  to 
the  muscles  whose  relationship  to  each  other  is  such  as 
to  render  it  difficult  for  them  to  so  relate  the  eyes  as  to 
make  binocular  vision  possible.  "Heterotropia"  is  a 
generic  term,  and  includes  all  forms  of  deviation  of  the 
visual  axes  and  the  vertical  axes  of  the  eyes;  ' '  esotropia  " 
means  that  there  is  a  deviation  of  the  visual  axes  in- 
ward, so  that  they  cross  each  other  between  the  observer 


498  HETEROTROPIA. 

and  the  point  of  observation;  "exotropia"  means  that 
there  is  an  outward  deviation  of  the  visual  axes,  so  that 
they  either  cross  beyond  the  point  of  view  or  become  par- 
allel, or  even  become  divergent;  "  hypertropia  "  means 
that  one  visual  axis  is  raised  above  the  other,  while 
"catatropia"  means  that  one  visual  axis  is  turned  be- 
low the  other;  "  cyclotropia "  means  that  the  vertical 
axes  of  the  eyes  are  not  kept  parallel  with  the  median 
plane  of  the  head,  either  diverging*  from  it  above  (plus 
cyclotropia)  or  converging  toward  it  above  (minus  cyclo- 
tropia). One  form  of  heterotropia  may  be  complicated 
by  one  or  more  of  the  other  forms. 

As  taught  in  Chapter  I.  of  this  book,  binocular  sin- 
gle vision  is  possible  only  when  the  superior  and  infe- 
rior recti  muscles  keep  the  two  visual  axes  in  the  same 
plane;  when  the  internal  and  external  recti  so  control 
these  axes,  in  that  plane,  as  to  make  them  intersect  at 
the  point  of  view;  and  when  the  superior  and  inferior 
obliques  parallel  the  vertical  axes  of  the  eyes  with  the 
median  plane  of  the  head.  These  muscles  accomplish 
this  work  in  obedience  to  the  unalterable  law  of  corre- 
sponding retinal  points.  Disobedience  on  the  part  of 
these  muscles  develops  diplopia,  for  the  reason  that  the 
two  images  of  the  one  object  cannot  fall  on  correspond- 
ing retinal  points.  That  objects  are  not  always  seen 
double  by  persons  who  have  any  form  of  heterotropia 


HETEROTROPIA.  499 

can  be  due  to  nothing-  else  than  mental  suppression  of 
one  image. 

Before  entering-  minutely  into  the  study  of  heterotro- 
pia,  it  will  be  interesting-  to  review,  briefly,  its  history. 
That  the  condition  has  existed  in  every  g-eneration  from 
the  beginning-  of  the  human  family,  can  hardly  be  doubted. 
What  it  was  interpreted  to  mean  in  ancient  times  cannot 
now  be  known.  Hippocrates  wrote  of  the  deformity  as 
a  thing  of  inheritance,  but  sometimes  resulting  from  dis- 
ease. From  the  time  of  his  writing,  on  down  through 
the  centuries,  there  is  no  evidence  of  any  careful  or  scien- 
tific study  of  heterotropia  until  in  the  second  quarter  of 
the  nineteenth  century.  About  this  time  Stromeyer  an- 
nounced that  strabismus  was  due  to  abnormal  contrac- 
tions of  the  eye  muscles,  and  that  it  might  be  cured  by 
tenotomies.  He  performed  experimental  tenotomies  on 
the  dead  subject  to  his  satisfaction.  One  year  later,  in 
1839,  Dieffenbach  operated  on  his  first  case  of  internal 
squint,  dividing  the  tendon  of  the  internal  rectus  close  to 
its  attachment  to  the  sclera.  He  thus  continued  to  op- 
erate throiigh  a  lengthy  series  of  cases.  Other  German 
surgeons,  and  surgeons  in  France  and  England,  began 
at  once  to  accept  the  teaching  of  Stromeyer  and  to  adopt 
the  practice  of  Dieffenbach.  After  the  French  Academy 
of  Sciences  had  awarded  its  prize  of  six  thousand  francs 
—half  to  Stromeyer  for  conceiving  the  operation  and 


500  HETEROTROPIA. 

demonstrating'  it  on  the  dead  subject,  and  half  to  Dieffen- 
bach  for  having  first  operated  on  the  living  subject  by 
cutting  the  tendon  of  the  muscle  close  to  its  attachment 
to  the  sclera — Dieffenbach  himself  led  in  the  bad  prac- 
tice of  cutting  the  tendon  farther  back.  He  reasoned 
that  the  farther  from  the  insertion  the  cut  was  made, 
the  greater  would  be  the  effect,  and  by  this  reasoning  he 
was  induced,  in  severe  cases,  to  make  the  cut  through 
the  muscle  structure  itself.  So  disastrous  were  these 
myotomies,  or  tenotomies  far  behind  the  insertions  of  the 
tendons,  that  the  operation  for  strabismus  began  to  fall 
into  disrepute.  It  required  the  master  mind  of  Graefe 
to  check  the  tide  of  professional  feeling  against  tenot- 
omies of  the  recti  muscles.  His  voice  called  operators 
back  to  the  original  operation  of  Dieffenbach,  after  which 
external  squints  were  less  frequently  found  as  a  result 
of  operations  for  internal  squint,  and  once  more  the  op- 
eration came  into  favor.  Graefe  even  went  farther  in 
the  direction  of  safety  than  a  simple  return  to  the  Dief- 
fenbach original  tenotomy,  in  that  he  advised  partial 
tenotomies  in  the  slighter  cases.  He  even  made  mar- 
ginal tenotomies,  but  apparently  these  were  done  em- 
pirically; at  any  rate,  he  did  not  give  any  reason  for 
doing  these  marginal  operations,  other  than  that  the  un- 
cut fibers  would  prevent  the  muscle  from  retracting  too 
far.  If  done  empirically,  while  some  of  them  may  have 


HETEROTROPIA.  501 

been  helpful,  others  must  have  been  hurtful,  because  of 
the  wrong-  kind  of  torsioning-  resulting-.  It  appears  that 
Graefe  abandoned  marg-inal  tenotomies,  possibly  because 
of  the  unfortunate  torsional  results  that  followed  in  many 
of  his  cases.  That  there  is  a  scientific — and,  therefore, 
sound — basis  for  marginal  tenotomies  has  already  been 
shown  in  previous  chapters,  and  will  be  set  forth  ag-ain, 
in  the  proper  place,  in  this  chapter.  It  would  also  appear 
that  Graefe  ceased  to  do  even  central  partial  tenotomies; 
for,  in  conversation  with  Knapp,  who  was  telling-  him  of 
these  operations  which,  thus  earl}"  in  his  professional 
career,  he  was  doing,  he  said,  "You  will  not  do  that 
long-,"*  thus  indicating-  that  he  himself  had  already 
abandoned  the  practice  of  partial  tenotomies.  Yet  it 
will  be  shown  in  this  chapter  that  partial,  and  not  com- 
plete, tenotomies  only  should  be  done,  even  in  the  hig-her 
degrees  of  heterotropia. 

As  was  natural,  soon  after  Dieffenbach's  tenotomy 
operation  on  the  contracted  muscle  was  introduced,  ad- 
vancement of  the  relaxed  muscle  was  sug-g-ested  and 
practiced  by  Querin.  The  author  has  been  unable  to 
learn  the  exact  method  he  employed,  but  it  must  have 
been  very  crude  and  unsatisfactory.  A.  von  Graefe's 
improvement  of  Querin 's  operation  is  worthy  of  mention 
only  as  a  curiosity.  The  only  connection  that  the  ad- 

*See  Norris  and  Oliver,  Vol.  III.,  page  877. 


502  HETEROTROPIA. 

vancing  thread  had  with  the  eye  was  the  loop  which  he 
passed  through  the  end  of  the  severed  tendon;  for  the 
two  ends  of  the  thread  were  carried  across  the  cornea 
and  anchored  by  adhesive  plaster  to  the  nose,  if  the 
muscle  were  the  externus,  and  to  the  temple,  if  it  were 
the  internus,  to  be  advanced.  The  threads  in  contact 
with  the  cornea  occasionally  excited  suppuration  of  that 
structure,  and  for  this  reason  the  operation  was  aban- 
doned. 

The  elder  Critchett,  in  1862,  at  the  Heidelberg  Con- 
gress, made  public  his  "method  of  advancement  by 
stitching-  the  tendon  forward."  This  operation  as  de- 
scribed by  Knapp*  is  attended  by  unnecessary  trauma- 
tism,  and  is  not  comparable,  in  simplicity  and  ease  of 
execution,  with  the  advancement  operation  described  in 
Chapter  III.  of  this  book.  The  Critchett  operation  was 
adopted  at  once  by  Graefe,  who  was  glad  to  substitute 
it  for  his  own  method.  It  seems  not  to  have  been  in- 
tended by  Critchett  that  this  operation  should  supplant 
the  operation  of  tenotomy  for  the  cure  of  heterotropia, 
but  that  it  should  act  only  as  an  aid  to  the  tenotomy. 

Since  1878  L/andolt  has  been  an  earnest  advocate  of 
advancement  of  the  relaxed  muscle,  as  against  tenotomy 
of  the  contracted  muscle,  in  all  cases  of  heterotropia, 
and  as  the  years  have  gone  by  his  advocacy  of  advance- 

*See  Norris  and  Oliver,  Vol.  III.,  pages  871-72. 


HETEROTROPIA.  503 

ment  has  grown  stronger.  Except  for  the  greater  ease 
with  which  a  tenotomy  is  done,  as  contrasted  with  the 
advancement  of  a  muscle,  Landolt's  voice  would  have 
been  heard,  and  to  a  greater  extent  would  have  been 
heeded.  But,  strange  to  say,  while  Landolt  has  been 
opposing  with  all  his  might  the  cutting  of  the  tendons 
of  the  ocular  muscles,  the  tenotomists  have  found,  or 
think  they  have  found,  the  check  ligaments  of  the  recti 
muscles;  and  some  of  them,  not  content  with  completely 
severing  the  tendon,  have  dared  to  reach  back  with  the 
scissors  and  cut  these  checks.  That  there  are  connect- 
ive tissue  fibers  that  extend  from  these  muscles  to  the 
walls  of  the  orbit  cannot  be  denied,  but  they  must  be 
concerned  more  in  firmly  fixing  the  bed  of  fat  through 
which  the  muscles  pass,  than  with  the  action  of  the 
muscles,  by  either  hindering  or  helping  them.  The  dis- 
section accomplished  in  cutting  these  ligaments  can  but 
allow  a  greater  retraction  of  the  divided  tendon,  which 
often  proved  to  be  too  much  even  before  the  ligaments 
were  known  to  exist. 

The  only  important  suggestion  in  connection  with 
complete  tenotomies,  since  Graefe  called  operators  back 
to  the  insertion  of  the  tendon,  has  come  from  Panas;  but 
even  this  suggestion  does  not  redeem  the  operation  of 
complete  tenotomy  from  the  condemnation  laid  upon  it 
by  Landolt.  Panas  stretches  the  muscle  before  sever- 


504  HETEROTROPIA. 

ing"  its  tendon.  The  stretching  of  the  muscle  necessa- 
rily results  in  a  state  of  paresis  for  the  time  being,  and 
it  is  probable  that  it  takes  days  for  the  recovery  to  be 
effected.  A  paretic  muscle  when  cut  is  not  in  a  condi- 
tion to  retract  far,  hence  adhesive  inflammation  has  the 
opportunity  to  reattach  the  cut  end  of  the  tendon  to  the 
sclera  only  a  little  way  behind  the  line  of  its  original  at- 
tachment. Panas'  operation  is  the  only  safe  complete 
tenotomy  that  can  be  done,  but  it  is  doubtful  if  it  should 
ever  be  done.  Words  cannot  be  made  strong  enough 
to  condemn  a  complete  tenotomy  associated  with  a  cut- 
ting of  the  check  ligaments.  After  any  complete  tenot- 
omy, except  the  one  suggested  by  Panas,  the  operator  is 
exceedingly  fortunate  if,  in  a  few  months,  he  does  not 
find  a  condition  opposite  that  for  which  he  operated. 
Even  in  Panas'  operation  the  risk  of  limiting  the  verting 
power  of  the  muscle  is  too  great;  and  occasionally,  in 
spite  of  the  paresis  caused  by  the  stretching,  the  muscle 
will  retract  too  far  and  an  external  squint  will  replace 
the  former  internal  squint,  or  vice  versa. 

One  of  the  strange  things  connected  with  the  study  of 
the  ocular  muscles,  soon  after  Dieffenbach  did  his  first 
operation,  was  the  conclusion  that  the  inferior  oblique 
was  an  advertor  of  the  eye.  Certainly  its  origin,  course, 
and  insertion  gave  no  foundation  for  such  a  conclusion. 
Lucas,  in  his  little  book  on  "  The  Cure  of  Strabismus," 


HETEROTROPIA.  505 

published  in  1840,  says  on  page  8:  "The  action  of  the 
inferior  oblique  is  to  direct  the  eye  upward  and  in- 
ward." That  the  above  reference  to  the  inferior  oblique 
could  not  have  been  a  typographical  error  is  abundantly 
shown  in  other  parts  of  the  book.  On  page  15  the  fol- 
lowing sentence  occurs:  "  When  either  eye  is  drawn  out- 
ward by  the  action  of  the  external  rectus  muscle,  the 
other  is  directed  inward  by  the  action  of  the  inner  rectus 
and  inferior  oblique  muscles." 

That  the  inferior  obliques,  without  being  advertors, 
may  cause  a  condition  that  becomes  an  important  com- 
plication of  esotropia,  will  be  shown  later  in  this  chap- 
ter. 

It  is  not  uninteresting  to  study  the  work  of  a  quack, 
John  Taylor,  who  flourished  in  the  first  half  of  the 
eighteenth  century,  at  least  one  hundred  years  before 
Stromeyer  and  Dieffenbach.  He  evidently  found  the 
secret  of  some  cases  of  squint,  and  it  is  just  as  evident 
that  his  secret  was  kept  by  him  and  died  with  him.  He 
wrote  a  pamphlet,  entitled  "De  Vera  Causa  Strabismi," 
which  was  published  in  1738,  in  which,  it  is  said,  he 
exploited  his  cures  without  exposing  his  method  of  oper- 
ating. In  traveling  from  city  to  city  on  the  continent 
of  Europe,  distributing  his  pamphlet  as  a  means  of  ad- 
vertising, he  styled  himself  as  "Oculist  to  George  II.,  of 
England,"  whom  he  probably  had  never  seen;  and  when 


506  HETEROTROPIA. 

it    suited    him   better,   he   claimed    to  be    oculist  to    the 
Pope. 

Taylor  was  a  man  of  some  penetration;  but  he  must 
have  been  a  man  too  full  of  self-interest  to  give  to 
science  and  progress  the  benefit  of  his  insight.  He  lost 
his  opportunity  to  build  for  himself  a  monument  that 
would  have  been  to  his  enduring-  credit,  by  burying 
within  himself  the  knowledge  on  which  he  based  his 
practice  of  straightening  cross-eyes.  He  seems  not  only 
to  have  been  an  oculist,  but  a  general  surgeon  as  well, 
for  he  carried  about  with  him  a  dazzling  display  of  in- 
struments. His  methods  of  secrecy  and  his  disposition 
toward  self-display  must  have  disgusted  surgeons  of 
that  time,  so  that  they  avoided  him,  just  as  honorable 
medical  men  of  to-day  feel  disgraced  when  found  in 
company  with  a  quack.  It  appears,  however,  that  L/e- 
Cat  either  witnessed  an  operation  or  that  he  had  an  op- 
portunity to  question  Taylor,  for  he  says:  *"I  availed 
myself  of  the  freedom  which  he  accorded  me  to  inquire 
the  motive  for  an  operation  which  appeared  to  me  to  be 
absolutely  useless,  not  to  say  dangerous.  He  replied 
that  an  eye  only  squinted  because  the  equilibrium  be- 
tween its  muscles  was  destroyed,  and  that  to  reestablish 
this  equilibrium  it  was  only  necessary  to  weaken  the 

*See  Stevens'  address  before  the  Ophthalmological  Association,  as  published  in  "An- 
nals of  Ophthalmology,"  Vol.  VIII.,  No.  2. 


HETEROTROPIA.  507 

muscle  which  dominated  the  others,  and  this  is  what  he 
did  in  cutting-  one  of  the  nerve  filaments  which  was  dis- 
tributed to  this  too  powerful  muscle." 

Heuerman,  in  1756,  wrote:  "  Taylor  has  also  proposed 
to  cure  squinting  by  the  division  of  the  tendon  of  the 
superior  oblique  muscle  of  the  eye."  Another  writer 
says  that  Taylor  passed  a  silk  thread  through  a  fold  of 
conjunctiva  at  the  lower-inner  part  of  the  g-lobe,  and, 
drawing1  this  fold  forward  by  means  of  his  loop  of  thread, 
cut  it  with  a  pair  of  scissors.  The  location  of  this  con- 
junctival  cut  makes  it  appear  possible  that,  through  it, 
he  passed  his  scissors  with  the  point  of  one  blade  in  con- 
tact with  the  orbital  floor,  and  sufficiently  far  backward 
to  include  the  inferior  oblique  muscle,  which  he  may  have 
divided  by  closing-  the  blades  of  the  scissors;  or  through 
the  opening  he  may  have  passed,  in  a  skillful  way,  one 
blade  of  the  scissors  between  the  sclera  and  the  tendon 
of  the  internus  while  keeping-  the  other  blade  between 
the  conjunctiva  and  the  tendon,  and  thus  effected  the  di- 
vision of  this  tendon. 

Taylor  must  have  had  some  cures,  whatever  may  have 
been  the  nature  of  his  operation.  Simply  sealing  with 
plaster  the  eye  not  operated  upon,  for  a  few  days,  could 
not  have  effected  a  cure,  unaided.  There  is  no  evidence 
of  the  existence  of  a  nerve  fiber  far  forward  giving  to 
the  internus  a  part  of  its  power;  hence  it  is  reasonable 


508  HETEROTROPIA. 

to  conclude  that  he  purposely  made  a  misstatement  when 
he  told  L/eCat  that  his  operation  was  a  division  of  such 
a  fiber.  It  is  very  unlikely  that  any  case  of  internal 
squint  ever  had,  as  an  etiolog-ical  factor,  a  too  strong 
superior  oblique;  hence  it  is  not  probable  that  Taylor 
ever  divided  this  muscle.  That  a  too  strong-  inferior 
oblique  may  be  an  indirect  factor  in  the  production  of  a 
small  per  cent  of  cases  of  internal  squint  will  be  shown 
farther  on;  hence  it  is  not  unreasonable  to  suppose  that 
he  may  have  divided  this  muscle  in  some  of  his  opera- 
tions. To  have  done  so  when  this  muscle  elevated  the 
eye  and  torted  it  outward,  while  the  internus  turned  it 
in,  would  have  been  helpful,  if  not  entirely  corrective. 
A  simple  esotropia  could  not  have  been  thus  corrected; 
so  it  appears  possible  that  in  simple  cases  he  had  learned 
to  divide  only  the  internus.  Since  Taylor  left  nothing- 
descriptive  of  the  cause  (termed  by  him  "  Vera  Causa  ") 
of  esotropia,  and  failed  to  print,  either  in  pamphlet  or  lay 
press,  anything-  as  to  the  method  of  his  operation,  one 
can  only  surmise  what  he  really  thoug-ht  and  did.  It  is 
certain  that  a  whole  century  intervened  between  him  and 
Stromeyer,  during-  which  time  no  advance  was  made  in 
the  practical  study  of  the  errors  of  the  ocular  muscles. 

The  author  almost  feels  that  he  should  apolog-ize  for 
making-  any  reference  to  Taylor,  the  quack,  who  deserved 
contempt  while  living-  and  oblivion  after  death. 


HETEROTROPIA.  509 

A  more  pleasant  task  presents  itself  in  a  brief  study 
of  the  work  of  the  immortal  Bonders,  who  gave  so  much 
thought  to  the  etiology  of  heterotropia.  His  investiga- 
tion into  the  relationship  between  accommodation  and 
convergence  proved  conclusively  that  hyperopia  is  one  of 
the  factors  of  esotropia.  This  doctrine  is  almost  uni- 
versally accepted,  and  there  seems  to  be  absolutely  no 
room  for  doubting  its  truthfulness.  It  must  be  granted, 
however,  that  Bonders  placed  too  much  emphasis  on  this 
potent  factor.  If  hyperopia  were  even  the  chief  cause 
of  internal  squint,  the  cases  demanding  operative  inter- 
ference would  be  few  and  far  between.  Hyperopia  must 
occupy  a  secondary  place  as  a  causative  factor  of  esotro- 
pia; nevertheless,  it  is  an  important  place,  for  a  removal 
of  this  cause,  by  the  wearing  of  convex  lenses,  early  in 
childhood,  often  will  make  the  other  cause  or  causes  in- 
operative. The  world  is  indebted  to  Bonders  for  this 
knowledge,  and  for  acquiring  and  imparting  it  he  de- 
serves a  monument. 

Finally,  before  taking  up  systematically  the  study  of 
heterotropia,  it  may  be  stated  that  it  has  always  been  a 
matter  of  observation  that  some  cases  of  internal  squint 
became  cured  without  artificial  aid.  This  spontaneous 
cure  came  as  the  patients  grew  older,  and  doubtless  de- 
pended on  the  fact  that  the  brain-centers  controlling  the 
ciliary  muscles  no  longer  generated  so  great  an  impulse 


510  HETEROTROPIA. 

for  these  muscles,  as,  because  of  association,  would  have 
continued  to  over-excite  the  centers  controlling  the  in- 
terni.  The  diminished  nerve  impulse  coming-  to  the  in- 
terni  gave  the  externi  a  chance  to  swing-  the  visual  axes 
into  positions  of  harmony.  It  is  not  explainable  how 
other  forms  of  heterotropia  could  ever  recover  spontane- 
ously, and  it  is  doubtful  if  they  ever  have  thus  recovered. 
As  early  as  the  seventh  century  of  the  Christian  era 
an  appliance  was  devised  for  straightening  cross-eyes. 
It  consisted  of  a  mask  with  a  hole  in  it  for  each  eye, 
which  the  patient  was  compelled  to  wear.  There  may 
have  been  some  cures,  but  the  annoj^ance  to  the  wearer 
must  have  been  great.  The  practice  may  have  been 
abandoned,  but,  if  so,  it  was  revived  again  by  Pare  in 
the  sixteenth  century. 

CLASSES  OF  HETEROTROPIA. 

There  are  two  classes  of  heterotropia — the  one  occur- 
ring at  any  period  of  life,  and  always  due  to  paralysis 
or  paresis  of  one  or  more  of  the  ocular  muscles,  and 
practically  always  curable  by  medication;  the  other  oc- 
curring in  infancy  or  early  childhood,  and  never  caused 
by  either  paralysis  or  paresis.  The  former  will  be  stud- 
ied in  Chapter  XI.,  where  the  means  of  making  a  differ- 
ential diagnosis  will  be  set  forth.  It  will  be  studied  as 
paralytic  heterotropia. 


HETEROTROPIA.  511 

COMITANT  HETEROTROPIA. —  Of  this  condition  there 
are  the  several  varieties  that  have  already  been  men- 
tioned, each  of  which  will  be  studied  separately  from 
the  standpoint  of  both  etiology  and  treatment.  In  lat- 
eral heterotropia,  although  the  visual  axes  are  not  prop- 
erly related— either  crossing-  within  the  point  of  view, 
as  in  esotropia,  or  crossing-  beyond  the  point  of  view, 
often  being-  parallel,  or  even  divergent,  as  in  exotropia — 
the  two  eyes,  nevertheless,  are  made  to  move  equally 
far  directly  to  the  rig-lit  or  left,  or  in  any  oblique  direc- 
tion— that  is,  the  one  visual  axis  accompanies  the  other 
in  every  movement,  in  any  direction,  the  degree  of  varia- 
tion from  the  normal  always  remaining-  the  same.  In  ver- 
tical heterotropia  one  visual  axis  rises  above  the  other,  as 
in  hypertropia,  or  one  visual  axis  falls  below  the  other, 
as  in  catatropia;  but  when  the  two  eyes  are  rotated  di- 
rectly up  or  down,  or  in  any  oblique  direction,  the  ang-le 
of  deviation  always  remains  the  same.  In  comitant  cy- 
clotropia,  it  is  reasonable  to  suppose  that  the  vertical 
axes  diverg-e  or  converg-e  the  same  in  all  movements  of 
the  visual  axes.  No  better  word,  therefore,  could  be 
chosen  for  defining-  these  conditions  than  "  comitant." 
The  old  term,  "concomitant,"  is  probably  neither  better 
nor  worse  than  the  shorter  term  adopted  by  Maddox, 
Jackson,  and  other  authors. 

The  term  ' '  comitant "  would  not  be  needed  except  that 


512  HETEROTROPIA. 

it  makes  it  easy  to  distinguish  true  heterotropia  from 
paralytic  heterotropia.  In  the  discussion  of  the  latter  in 
the  next  chapter,  it  will  be  shown  that,  in  some  one  part 
of  the  field  of  rotation,  the  visual  axes  will  be  properly 
related,  giving  binocular  single  vision,  whatever  muscle 
maybe  paralyzed;  while  rotation  in  the  opposite  part  of 
the  field  will  be  attended  by  a  lagging  behind  of  the 
visual  axis  of  the  eye  to  which  the  affected  muscle  be- 
longs, which  will  always  be  shown  by  diplopia,  and  often 
may  be  detected  by  the  observer.  Diplopia,  under  ordi- 
nary conditions,  does  not  manifest  itself  in  comitant 
heterotropia,  for  the  reason  that  the  occurrence  of  the 
error  early  in  life  made  it  possible  for  the  mind  to  sup- 
press the  images  in  the  wrongly-directed  eye  that  other- 
wise would  have  interfered  with  objects  seen  by  the 
properly-directed  eye.  Equal  deviation  in  all  positions 
of  the  eyes  and  no  diplopia  means  comitant  heterotropia; 
unequal  deviations — none  at  all  in  one  direction,  but 
greater  or  less  in  the  opposite  direction,  with  single  vi- 
sion, in  one  part  of  the  field  and  diplopia  in  the  opposite 
part — mean  paralytic  heterotropia.  In  the  former  there 
is  no  disturbance  of  locomotion,  while  in  the  latter  the 
patient  becomes  more  or  less  dizzy.  In  the  former,  the 
secondary  deviation  is  equal  to  the  primary  deviation;  in 
the  latter,  the  secondary  deviation  is  always  greater  than 
the  primary. 


ESOTROPIA.  513 

The  etiology  of  comitant  heterotropia  can  be  studied 
to  better  advantage  in  the  discussion  of  the  individual 
varieties. 

COMITANT  ESOTROPIA. — This  condition — known  also 
as  internal  strabismus,  internal  squint,  and  cross-eyes 
— is  the  most  common  form  of  heterotropia.  It  always 
occurs  in  early  life,  usually  at  the  age  of  two  or  three 
years.  The  conditions  causing1  the  error  exist  from 
birth,  and  only  one  of  the  several  natural  causes  un- 
dergoes any  change  at  any  time  after  birth.  In  the 
greater  number  of  cases  it  is  the  character  of  the  nerve 
impulse  to  the  ciliary  muscles  that  causes  over-stimula- 
tion of  the  third  conjugate  innervation  center,  which 
over-stimulation  causes  an  actual  deviation,  when  pre- 
viously there  was  only  a  tendency  toward  deviation — a 
conversion  of  an  esophoria  into  an  esotropia.  Why  this 
change  should  not  occur  earlier  than  the  second  or  third 
year  is  variously  explained.  Usually  authors  are  agreed 
that  children  look  at  near  objects  but  little  until  two 
years  old,  at  which  time  they  begin  to  take  interest  in 
toys  and  pictures,  looking  intentl}r  at  them,  at  close 
range.  Children  who  become  esotropic  are  nearly  al- 
ways hyperopic,  hence  are  forced  to  use  their  ciliary 
muscles  in  far  vision,  which  means  that,  in  near  vision, 
an  excessive  nerve  impulse  must  be  generated  and  sent 
to  these  muscles.  A  correspondingly  increased  impulse 


514  ESOTROPIA. 

is  sent  to  the  intern!,  which  are  naturally  too  strong-  for 
the  externi,  and  the  eyes  cross. 

Maddox  teaches  in  his  work,  * '  The  Ocular  Muscles, ' ' 
that  the  lenses  increase  in  density  even  in  infancy,  and 
by  the  time  the  child  is  two  or  three  years  old  a  greater 
impulse  is  needed  by  the  ciliary  muscles  to  effect  the 
necessary  change  in  the  convexity  of  the  lenses.  This 
increase  of  ciliary  impulse  is  attended  by  a  corresponding- 
increase  of  the  converg-ence  impulse,  which  develops  the 
esotropia.  This  would  occur  whether  the  child  were 
hyperopic  or  emmetropic.  An  acceptance  of  either  ex- 
planation throws  the  immediate  blame  for  the  crossing- 
of  the  eyes  on  the  ciliary  muscles. 

Whatever  may  be  the  reason  for  the  short  delay  in 
the  manifestation  of  esotropia,  there  must  be  a  cause  or 
causes  that  finally  develop  the  condition.  The  follow- 
ing- factors  will  be  discussed  in  the  order  of  their  im- 
portance: Esophoria,  hyperopia,  hyperphoria  of  one  eye 
and  cataphoria  of  the  other;  a  lower  state  of  visual 
acuity  in  one  eye  than  in  the  other,  either  from  some 
cong-enital  abnormality  in  the  perceptive,  transmitting-, 
or  receptive  part  of  the  apparatus,  or  some  opacity  or 
irreg-ularity  of  the  refractive  media,  either  cong-enital  or 
the  result  of  disease,  or  because  there  is  a  greater  error 
of  refraction  in  one  eye  than  in  the  other.  Finally, 
the  whole  of  the  macula  in  one  eye  may  be  connected 


ESOTROPIA.  515 

with  one  side  of  the  brain,  while  the  whole  of  the  macula 
in  the  other  eye  may  be  connected  with  the  other  side  of 
the  brain.  A  sixth  complication,  if  not  a  cause,  is  a  plus 
or  minus  cyclophoria. 

ESOPHORIA  AS  A  CAUSE. — It  is  safe  to  say  that  with- 
out esophoria  there  can  be  no  esotropia;  but  ordinarily 
esophoria  must  be  aided  by  one  or  more  of  the  other 
causes  in  the  production  of  esotropia.  Esophoria,  when 
high  in  degree,  may  eventuate  in  esotropia,  and  at  the 
usual  age  or  earlier,  when  there  is  no  hyperopia,  even 
when  the  refractive  error  is  myopic.  When  esophoria 
alone  is  the  cause  of  esotropia,  the  actual  turning  occurs 
when  the  externi,  always  too  weak  as  compared  with  the 
interni,  give  up  the  task  of  so  antagonizing  the  interni 
as  to  make  binocular  vision  possible.  At  this  time  the 
mind  selects  one  eye  for  use,  and  the  other  is  allowed  to 
turn  into  the  position  predetermined  by  the  excessive 
power  of  its  internus.  If  its  plane  of  action  coincides 
with  the  horizontal  plane  of  the  eye,  the  position  as- 
sumed will  be  directly  in  toward  the  nose;  if  the  plane 
of  its  action  is  elevated,  its  attachment  being  too  high, 
the  eye  will  turn  up  as  well  as  in  and  will  be  torted  in; 
but  if  its  plane  of  rotation  is  depressed,  its  attachment 
being  too  low,  the  eye  will  be  turned  down  as  well  as  in, 
and  will  be  torted  out.  At  the  time  of  the  beginning  of 
the  in-turning,  the  mind,  in  the  interest  of  single  vision, 


516  ESOTROPIA. 

begins  the  work  of  suppressing  the  images  on  the  retina 
of  the  in-turned  eye.  If  the  esotropia  is  not  periodic  or 
alternating,  the  work  of  mental  suppression  is  soon 
accomplished,  the  patient  becoming  mind-blind  in  the 
crossed  eye.  When  an  esophoria  alone  is  the  cause  of 
esotropia,  the  error  probably  shows  itself  earlier  than 
usual.  Spontaneous  recovery,  in  such  a  case,  will  never 
occur.  For  a  study  of  esophoria,  the  reader  is  referred 
to  Chapter  IV.  of  this  book. 

HYPEROPIA  AS  A  CAUSE. — When  hyperopia,  or  hy- 
peropic  astigmatism,  is  one  of  the  causes  of  esotropia, 
it  is  not  the  quantity  of  the  error,  but  the  character  of 
the  required  impulse  for  its  correction,  that  enters  as  a 
factor.  A  greatly  excessive  impulse  may  be  needed  for 
the  correction  of  a  small  error,  while  an  impulse  not  so 
great  gets  a  more  ready  response  on  the  part  of  the  cil- 
iary muscles  for  the  correction  of  a  greater  error.  The 
excessive  activity  of  the  center  for  the  ciliary  muscles 
causes  over-excitation  of  the  third  conjugate  center,  thus 
developing  a  pseudo-esophoria.  This  grafted  on  an  in- 
trinsic esophoria  may  readily  convert  it  into  an  esotropia. 
The  foundation  for  every  permanent  esotropia  is  intrinsic 
esophoria.  An  esotropia  caused  by  hyperopia  alone  will 
be  periodic,  and  never  permanent.  In  such  cases,  sup- 
pression of  images  is  impossible.  In  cases  of  esotropia, 
in  which  spontaneous  recovery  takes  place,  hyperopia  has 


ESOTROPIA.  517 

been  the  chief  cause.  If  the  esotropia  spontaneously 
cured  has  lasted  very  long,  mental  suppression  has  ac- 
complished its  work,  and  the  eye  once  crossed  remains 
low  in  visual  acuity. 

The  position  assumed  by  an  esotropic  eye  when  the 
two  factors,  esophoria  and  hyperopia,  have  acted  to- 
gether, is  always  determined  by  the  character  of  attach- 
ment the  internal  rectus  may  have.  The  eye  may  be 
turned  straight  in,  or  in  and  up  with  inward  torsion  ing, 
or  in  and  down  with  outward  torsioning. 

The  esophoria  unassociated  with  hyperopia,  in  many 
cases,  would  not  have  caused  esotropia;  hence  it  ap- 
pears reasonable  to  conclude  that  a  correction  of  the 
hyperopia  would  result  in  a  reconversion  of  the  esotro- 
pia back  into  esophoria.  This  is  just  what  is  accom- 
plished in  a  large  per  cent  of  the  cases  of  esotropia  that 
are  brought  early  to  the  oculist.  Thus  cross-e}Tes  are 
straightened  without  operation;  but  this  does  not  mean 
that  an  operation  may  not  be  required  later  for  the  cure 
of  the  esophoria,  for  the  relief  of  reflex  troubles. 

HYPERPHORIA  AND  CATAPHORIA  AS  CAUSES. — The 
plane  of  action  of  the  superior  and  inferior  recti  is  such 
that  they  not  only  turn  the  eyes,  respectively,  up  and 
down,  but  they  also  turn  them  in.  Imbalance  of  the 
superior  and  inferior  recti,  whether  that  imbalance  is 
shown  in  a  hyperphoria  of  one  eye  and  a  cataphoria  of 


518  ESOTROPIA. 

• 

the  other,  or  in  a  double  hyperphoria  or  in  a  double 
cataphoria,  will  become  a  factor  in  the  production  of  eso- 
tropia  only  when  there  is  an  esophoria.  When  these 
two  causes  act  together,  the  crossing"  will  occur  at  the 
usual  age  (in  the  second  or  third  year);  but  the  esotro- 
pia  will  be  complicated  by  a  hypertropia  or  catatropia. 
If  there  is  an  eso-hypertropia  and  the  superior  rectus 
is  the  cause  of  the  hypertropia,  there  will  be  a  minus 
cyclotropia  of  that  eye.  If  the  fellow  eye  becomes  eso- 
catatropic  under  cover  and  the  catatropia  is  caused  by 
the  inferior  rectus,  there  will  be  a  plus  cyclotropia  of 
this  eye.  In  double  eso-hypertropia,  the  hypertropia 
being  caused  by  the  superior  recti,  there  will  be  also  a 
minus  cyclotropia  of  each  eye;  and  in  double  eso-cata- 
tropia,  the  catatropia  being  caused  by  the  inferior  recti, 
there  will  be  also  a  plus  cyclotropia.  When,  in  eso- 
hypertropia,  the  hypertropia  is  effected  by  both  the  su- 
perior rectus  and  the  inferior  oblique,  there  will  be  no 
cyclotropia;  when,  in  eso-catatropia,  the  catatropia  is 
caused  by  both  the  inferior  rectus  and  the  superior  ob- 
lique, there  will  be  no  cyclotropia. 

There  are  cases  of  double  eso-hypertropia,  in  which 
there  is  marked  plus  cyclotropia,  easily  observed  without 
instrumental  aid.  The  cause  of  the  hypertropia  in  these 
cases  is  to  be  found  in  the  inferior  obliques,  which  mus- 
cles also  cause  the  plus  cyclotropia.  In  these  cases  the 


ESOTROPIA.  519 

esotropia  is  wholly  due  to  the  interni.  That  the  turn- 
ing- up  is  not  helped  by  the  interni  is  shown  by  the  ex- 
istence of  the  plus  cyclotropia;  for,  while  a  too  high  in- 
ternus  will  turn  the  eye  up,  it  will  not  tort  it  out.  Thus 
it  appears  that  a  hyperphoria,  caused  by  the  inferior  ob- 
liques, cannot  be  a  direct  factor  in  the  causation  of  eso- 
tropia. If  not  a  cause,  it  must  be  considered  as  a  most 
important  complication.  The  possible  factors  of  esotro- 
pia and  its  complications  can  be  found  only  by  means  of 
a  most  painstaking-  examination  with  the  phorometer, 
cyclo-phorometer,  and  tropometer,  or  perimeter. 

Low  STATE  OF  VISUAL  ACUITY  AS  A  CAUSE. — This 
condition,  whatever  may  be  its  cause,  can  be  only  a 
secondary  factor  in  the  production  of  esotropia;  for  in 
these  cases,  as  in  all  others,  esophoria  is  the  chief  factor. 
If  the  low  visual  acuity  is  due  to  some  congenital  condi- 
tion, or  is  caused  by  disease  or  injury  in  early  infancy, 
the  esophoria  will  be  transformed  into  esotropia  in  early 
life.  If  both  eyes  have  been  g-ood  for  any  number  of 
years,  when  disease  or  injury  renders  the  vision  of  one 
eye  bad,  or  even  destroys  vision  altogether,  this  eye  will 
become  esotropic,  if  esophoria  has  previously  existed;  if 
there  is  no  esophoria,  there  can  be  no  esotropia,  however 
low  may  become  the  vision  of  one  eye.  An  eye  that  be- 
comes blind  will  continue  to  move  in  harmony  with  its 
fellow,  if  previously  there  has  been  no  form  of  hetero- 


520  ESOTROPIA. 

phoria.  If  there  is  known  to  be  a  certain  kind  of  imbal- 
ance of  the  muscles  when  the  vision  in  both  eyes  is  good, 
should  the  vision  of  one  eye  be  much  reduced,  or  even 
lost,  a  positive  prediction  can  be  made  as  to  the  kind  of 
heterotropia  that  will  result:  the  turning  will  always  be 
in  the  direction  of  the  tendency.  If  there  is  perfect  bal- 
ance of  all  the  ocular  muscles,  diminution,  or  loss,  of 
vision  of  one  eye  will  not  interfere  with  the  harmonious 
movements  of  the  two  eyes;  a  blind  e}Te,  under  perfect 
muscle  adjustment,  will  always  appear  to  fix  the  object 
seen  with  the  good  eye. 

FAULTY  CONNECTION  OF  THE  MACULAS  WITH  THE 
BRAIN  AS  A  CAUSE. — There  are  cases  of  esotropia  in 
which  it  is  impossible  to  fuse  the  two  images  of  an  ob- 
ject. Such  cases  were  observed  by  Graefe,  who  defined 
the  condition  as  "antipathy  to  binocular  single  vision." 
The  cause  of  this  antipathy,  in  all  probabilit}T,  is  that 
the  macula  of  one  eye  is  connected  with  one  side  of  the 
brain,  while  the  macula  of  the  fellow  eye  is  connected 
with  the  other  side  of  the  brain.  To  fuse  images  on  the 
two  maculas  their  impressions  must  be  carried  to  the 
same  side  of  the  brain,  which  cannot  be  accomplished  un- 
less the  nerve  fibers  passing  from  the  two  maculas  find 
their  way  into  the  same  optic  tract  and  thence  go  to  the 
same  cuneus.  If  the  maculas  fail  to  have  a  common  con- 
nection with  the  brain,  other  retinal  points  that  ought  to 


ESOTROPIA.  521 

correspond  cannot  do  so,  and  there  must  be  diplopia  in 
all  parts  of  the  field.  The  condition,  if  it  exists,  is  con- 
genital, and  the  only  reason  why  there  is  not  annoying 
diplopia  must  be  due  to  the  habit  of  mental  suppression 
acquired  in  infancy.  Esotropia  due  to  such  a  cause 
must  occur  earlier  in  life  than  is  usual,  possibly  within 
the  first  few  \veeks  after  birth. 

Pathology  points  to  the  possibility  of  such  a  cause  for 
esotropia.  A  disease  involving  the  center  of  sight  in 
one  cuneus,  or  a  disease  involving  all  the  nerve  fibers 
as  they  pass  from  one  cuneus  in  their  course  to  the  optic 
chiasm,  whether  in  the  tract  or  farther  back,  must  cause 
hemianopsia,  involving  corresponding  halves  of  the  two 
retinas,  the  temporal  half  of  one  retina  anc  the  nasal 
half  of  the  other.  Many  such  cases  have  been  observed. 
In  some  cases  the  line  dividing  the  blind  part  from  the 
seeing  part  of  each  retina  has  been  vertical,  passing 
down  through  the  macula;  in  other  cases,  while  these 
lines  were  vertical,  they  missed  the  maculas,  passing  a 
few  degrees  either  to  the  right  or  to  the  left  of  both,  the 
two  maculas  falling  either  in  the  blind  or  in  the  seeing 
parts,  in  either  case  showing  that  both  were  connected 
with  the  same  side  of  the  brain;  in  other  cases  the  divid- 
ing lines  have  not  been  vertical,  the  obliquity  being  some- 
times as  much  as  ten  degrees,  but  the  same  in  the  two 
eyes.  The  oblique  lines  have  passed,  in  the  reported 


522  ESOTROPIA. 

cases,  either  through  the  maculas  or  have  fallen  on  cor- 
responding- sides.  No  case,  so  far  as  the  author  knows, 
has  ever  been  reported  showing  that  the  blindness  in 
the  temporal  half  of  one  retina  included  the  macula, 
while  the  blindness  in  the  nasal  half  of  the  other  retina 
did  not  include  the  macula,  else  no  further  argument 
would  be  necessary.  That  pathology  has  shown  no 
cases  of  faulty  connection  of  the  maculas  with  the 
brain  is  probably  due  to  the  rarity  of  the  condition- 
certainly  as  rare  as  is  "antipathy  to  binocular  single 
vision,"  for  the  one  must  be  a  synonym  of  the  other.  If 
the  lines  dividing  the  retinas  into  two  halves  pass,  in 
some  cases,  down  through  the  maculas,  while  in  other 
cases  both  these  lines  pass  either  to  the  right  or  to  the 
left  of  the  maculas,  it  must  be  conceded  as  a  possibility 
that  the  dividing  line  in  one  retina  may  pass  to  the  right 
of  the  macula,  while  the  dividing  line  in  the  other  retina 
may  pass  to  the  left  of  the  macula.  In  this  case  disease 
of  one  cuneus  or  of  one  tract  would  destroy  the  per- 
ceptive power  of  one  macula,  while  the  other  macula 
would  be  uninvolved.  There  being  no  disease  in  such 
a  case,  the  impress  of  an  image  on  one  macula  would  be 
conveyed  to  one  side  of  the  brain,  while  the  impress 
of  the  image  on  the  other  macula  would  be  sent  to 
the  other  side  of  the  brain,  and  there  could  be  no 
fusion  of  the  two.  So  far  as  the  author  can  see,  nothing 


ESOTROPIA.  523 

else  can  account  for  "antipathy  to  binocular  single 
vision." 

Every  surgeon  of  much  experience  with  esotropia  has 
had  cases  that  he  could  not  cure,  however  skilled  as  an 
operator.  Each  attempt  to  correct  the  error  in  such  a 
case  makes  the  patient  worse,  for  the  reason  that,  under 
the  old  condition,  the  power  of  suppression  of  images  in 
one  eye  had  been  acquired,  while  under  the  new  condi- 
tion, the  images  fall  on  new  parts  of  the  retina  of  the 
eye  operated  upon,  and  diplopia  is  at  once  made  manifest. 
The  more  nearly  the  readjustment  of  the  muscles  brings 
the  eyes  straight — to  exactly  straighten  them  is  impos- 
sible— the  more  annoying  becomes  the  diplopia.  If  the 
patient  is  mature  at  the  time  the  operation  is  done,  his 
diplopia  will  always  be  annoying,  for  he  can  never  re- 
acquire  the  power  of  mental  suppression.  To  have  let 
such  a  patient  alone  would  have  been  a  mercy. 

Fortunately,  esotropia  due  to  the  cause  under  discus- 
sion is  rare.  That  the  mistake  of  operating  on  such 
cases  may  not  be  made,  the  operator  should  give  most 
careful  study  to  every  case.  When  there  is  great  am- 
blyopia  of  the  esotropic  eye,  one  may  feel  fairly  sure 
that  the  case  is  not  of  this  character;  for  usually  a  case 
of  this  kind  has  fairly  good  vision  in  either  eye  when  the 
other  is  excluded,  for  the  esotropia  is  alternating.  But 
all  cases  of  alternating  esotropia,  with  fairly  good  vi- 


524  ESOTROPIA. 

sion  in  each  eye,  do  not  belong  to  this  hopeless  class.  In 
any  case  of  esotropia  the  fusion  test  should  be  applied; 
but  in  alternating*  esotropia  this  test  becomes  absolutely 
essential.  When  the  images  can  be  fused,  the  case  can 
be  cured;  if  the  images  cannot  be  fused,  a  cure  is  im- 
possible, and  should  never  be  attempted.  The  method 
of  making  the  fusion  test  will  be  given  farther  on,  and 
the  peculiar  play  of  images  that  cannot  be  fused  will  be 
shown. 

The  varieties  of  comitant  esotropia  have  already  been 
mentioned  incidentally.  They  may  be  grouped  here  as 
follows:  Periodic,  alternating,  and  permanent.  The 
same  case,  at  different  times,  may  present  these  different 
conditions.  Periodic  esotropia  is  always  curable;  while 
alternating  esotropia  may  be  curable,  it  is  always  open 
to  the  suspicion  that  there  is  ' '  antipathy  to  binocular 
single  vision."  Permanent  esotropia  is  usually  attended 
by  pronounced  amblyopia  in  the  deviating  eye,  and  prac- 
tically always  depends  on  causes  that  can  be  relieved. 
Occasionally  a  case  of  permanent  esotropia  may  belong 
to  the  incurable  class,  in  which  there  is  "antipathy  to 
binocular  single  vision." 

Comitant  esotropia  must  be  differentiated  from  appar- 
ent esotropia  and  from  paretic  esotropia.  The  cover 
test  at  once  settles  the  question  as  to  apparent  esotropia, 
for,  on  covering  and  uncovering  the  eyes  alternately, 


ESOTROPIA.  525 

there  will  be  no  resetting-  of  either  eye,  both  visual  axes 
always  pointing  toward  the  test  object.  The  cover  test, 
in  comitant  esotropia,  always  shows  a  resetting1  of  both 
eyes  when  covered  and  uncovered  alternately.  Under 
this  test  there  are  always  present  the  primary  and  the 
secondary  deviations — the  one  equal  to  the  other.  In  pa- 
retic  esotropia  the  secondary  deviation  is  always  greater 
than  the  primary  deviation,  for  the  reason  that  if  the 
paretic  muscle  is  the  right  externus,  the  fourth  con  ju- 
g-ate innervation  center  sends  an  excessive  impulse  to 
the  right  externus,  because  it  is  paretic,  and  to  the  left 
internus,  causing1  the  latter  to  manifest  excessive  power. 
On  covering-  the  paretic  eye  and  uncovering  the  good 
eye,  the  fifth  conjugate  innervation  center  sends  only 
an  ordinary  impulse  to  the  left  externus  and  the  right 
internus,  hence  the  slighter  deviation  of  the  eye  to  which 
belongs  the  paretic  muscle. 

The  complications  of  esotropia  are:  hypertropia  of  one 
eye  and  catatropia  of  the  other,  double  hypertropia, 
double  catatropia,  and  cyclotropia.  Hyperopia  and  hy- 
peropic  astigmatism  may  also  be  considered  as  compli- 
cations. In  the  treatment  of  esotropia,  it  is  essential 
that  all  these  complications  shall  be  either  found  or 
excluded. 

THE  FUSION  TEST. — There  is  no  test,  in  the  investi- 
gation of  a  case  of  comitant  esotropia,  so  important  as 


526  ESOTROPIA. 

the  fusion  test.  The  ability  to  fuse  images  should  be 
determined,  regardless  of  the  time  it  may  take.  If  a  pa- 
tient could  be  made  conscious  of  double  vision  at  once,  the 
ability  to  fuse  could  be  quickly  found.  The  test  object 
should  be  a  candle  or  a  gas  jet.  Placing  a  red  glass  be- 
fore the  good  eye,  the  natural  light  is  often  easily  found 
by  the  deviating  eye,  and  on  the  corresponding  side.  If 
the  red  glass  before  the  good  eye  does  not  bring  out  the 
consciousness  of  the  double  candle,  then  a  green  or  a 
blue  glass  ma}r  be  held  before  the  deviating  eye,  thus 
discoloring  both  images.  As  soon  as  the  two  discolored 
lights  are  seen,  the  glass  before  the  deviating  eye  may 
be  removed,  when,  with  comparative  ease,  the  natural 
light  is  seen  by  this  eye,  while  the  red  light  is  seen  by 
the  fellow  e}Te.  If  the  two  are  not  level,  they  should  be 
made  so  by  means  of  the  proper  prism,  placed  vertically. 
Now,  by  means  of  the  rotary  prism  before  the  deviating 
eye,  the  yellow  blaze  should  be  made  to  approach  the 
red  one.  If  they  are  more  than  ten  degrees  apart,  a 
supernumerary  prism  should  be  placed,  with  its  base 
out,  behind  the  rotary  prism,  when,  starting  again  at 
zero,  the  index  is  again  carried  into  the  nasal  quadrant; 
and  as  it  revolves,  the  lights  are  brought  nearer  and 
nearer,  until  finally  they  merge  into  one.  In  the  whole 
test,  the  fixing  eye  is  the  good  eye,  and  the  fixed  object 
is  the  red  light.  The  fusion  is  effected  the  moment  the 


ESOTROPIA.  527 

yellow  image  is  thrown,  by  prismatic  action,  on  the  mac- 
ula. Once  fused,  there  should  be  no  diplopia  so  long  as 
the  fusing  prisms  remain  unchanged.  Whenever  fusion 
is  found  possible,  the  case  is  curable. 

If  there  is  antipathy  to  binocular  single  vision,  the 
false  (yellow)  light  can  be  made  to  approach  the  true 
(red)  light,  but  cannot  be  made  to  fuse  with  it.  The 
two  will  "kiss"  and  then  recede,  or  the  one  will  rise 
above  or  fall  below  the  other  and  pass  to  the  opposite 
side.  Any  number  of  repetitions  of  the  effort  to  fuse,  by 
means  of  the  most  careful  use  of  the  rotary  prism,  will 
result  in  failure.  Such  a  case  is  incurable  by  any  and 
every  means;  and,  therefore,  no  attempt  should  be  made. 
Operations  certainly  make  these  cases  \vorse. 

Comitant  esotropia  is  a  monocular  trouble  only  in  ap- 
pearance. In  reality  it  is  binocular — a  fact  that  should 
always  be  remembered  when  operations  are  about  to  be 
done  for  its  relief.  The  binocular  character  of  esotropia 
is  shown  by  the  cover  test;  for  the  moment  the  deviating 
eye  is  made  to  fix,  because  the  good  eye  is  covered,  the 
latter  turns  in.  After  operations  have  been  done  on  the 
deviating  eye,  it  sometimes  becomes  easier  to  use  this  eye, 
at  which  time  the  fellow  eye  turns  in,  but  not  so  much  as 
the  original  eye  had  turned.  This  use  of  the  eye  that 
before  deviated,  favors  the  cure  of  the  amblyopia,  with- 
out detriment  to  the  other  eye. 


528  ESOTROPIA. 

MEASUREMENTS  OF  ESOTROPIA. 

There  are  several  methods,  some  more  accurate  than 
others,  but  all  of  them  of  some  value.  The  phorometer 
test  is  the  only  one  that  is  perfectly  correct;  and,  unfor- 
tunately, it  is  the  hardest  one  to  accomplish,  for  the  rea- 
son that  it  is  so  difficult  to  develop  consciousness  of  di- 
plopia.  If  diplopia  could  always  be  made  manifest,  the 
other  methods  of  measurement  would  soon  be  discarded. 
The  angle  gamma  does  not  interfere  with  the  phorometer 
test,  but  it  does  militate  against  all  other  tests.  This  an- 
gle is  formed  at  the  crossing  of  the  visual  axis  and  the 
line  commonly  called  the  "optic  axis,"  at  the  center  of 
the  retinal  curve,  which  is  the  center  of  rotation  of  the 
eye.  For  a  better  understanding  of  the  angle  gamma 
the  lines  whose  intersection  forms  it  should  be  studied. 
The  visual  axis  begins  always  at  the  fovea  centralis, 
and  must  always  pass  through  the  center  of  motion, 
which  is  the  center  of  retinal  curvature,  and  thence  it 
must  pass  through  the  cornea,  but  at  no  definite  point; 
it  may  be  its  center,  but  more  often  the  point  through 
which  the  visual  axis  passes  is  away  from  the  corneal 
center.  The  visual  axis  is  the  antero-posterior  axis  of 
rotation.  It  is  strange  how  the  line  of  fixation  should 
ever  have  been  conceived  as  other  than  the  visual  axis; 
and  yet  the  cut  in  Swanzy's  book,  edition  of  1900,  page 
25,  shows  the  visual  axis  passing  from  the  supposed 


ESOTROPIA.  529 

macula  through  the  nodal  point  out  to  an  object  in  space. 
The  same  cut  shows  the  line  of  fixation  extended  from 
the  object  in  space  to  the  center  of  rotation,  stopping 
there.  Had  he  extended  it  back  to  the  retina,  he  would 
have  missed  the  supposed  macula,  as  shown  in  his  cut; 
but  it  would  have  passed  to  the  real  macula,  for  the  line 
of  fixation  can  be  none  other  than  the  straight  line  that, 
passing  through  the  center  of  rotation,  connects  the  ob- 
ject and  its  image  on  the  macula.  The  so-called  "op- 
tic axis  "  is  the  line  that  must  begin  at  the  center  of  the 
cornea  and  must  pass  through  the  center  of  rotation  and 
may  reach  the  macula,  but  more  often  misses  it.  This 
line,  unless  it  coincides  with  the  line  of  fixation,  cannot 
be  an  axis  of  rotation,  for  the  reason  that  it  cannot  pass 
through  the  equatorial  plane  at  right  angles;  for  the  equa- 
torial plane  must  be  at  right  angles  to  the  line  of  fixation — 
the  visual  axis.  The  point  always  common  to  these  tsvo 
axes,  or  lines,  is  the  center  of  rotation  of  the  eye,  and  the 
angle  formed  by  their  intersection  is  the  angle  gamma. 
The  average  size  of  this  angle  is  about  five  degrees, 
though  in  an  ideal  eye  it  is  nothing.  When  this  angle  is 
to  the  nasal  side  of  the  visual  axis,  the  eye  that  is  straight 
would  appear  to  be  esotropic;  if  to  the  temporal  side, 
the  eye  would  appear  to  be  exotropic.  The  angle  is 
more  often  temporal  than  nasal;  hence  an  esotropia 
would  appear  less  than  it  really  is,  while  an  exotropia 


530  ESOTROPIA. 

would  be  exaggerated  by  it.  This  angle  can  always 
be  measured  by  the  perimeter,  and,  when  known,  can  be 
taken  from  or  added  to,  as  the  case  may  be,  the  esotro- 
pia  that  has  been  previously  measured  in  any  other  way 
than  by  the  phorometer. 

MEASUREMENT  BY  THE  PHOROMETER. — A  red  glass 
should  be  placed  before  the  good  eye.  Before  the  deviat- 
ing eye  should  be  placed  the  rotary  prism  in  the  position 
for  testing-  for  lateral  heterophoria,  with  the  displacing 
prism  of  six  degrees,  base  up,  in  the  cell  toward  the  eye. 
The  red  and  the  yellow  blazes  of  the  candle  or  gas  jet 
having  been  found,  the  latter  will  appear  more  or  less 
removed  from  the  vertical  line  passing  down  through  the 
red  light  and  in  the  direction  corresponding  to  the  de- 
viating eye.  The  fifteen-degree  supernumerary  prism 
should  be  placed,  base  out,  in  the  front  cell,  which  will 
carry  the  yellow  light  just  that  far  toward  the  vertical 
line  passing  through  the  red  light.  Revolving  the  rotary 
prism  in  the  nasal  arc,  the  yellow  light  is  carried  still 
nearer  the  vertical  line,  which  it  may  be  made  to  reach  at 
some  point  between  zero  and  ten  degrees;  but  if  this  falls 
short,  the  rotary  prism  should  be  revolved  back  to  zero, 
and  a  stronger  supernumerary  prism  (twenty  degrees, 
twenty-five  degrees,  or  thirty  degrees)  should  be  placed 
in  the  anterior  cell.  Now  the  rotary  prism  should  be 
turned  again  in  the  nasal  arc  and  then  stopped  at  that 


ESOTROPIA.  531 

point  where  the  patient  declares  the  yellow  light  direct- 
ly under  the  red  one.  If  the  twenty-five-degree  prism 
is  in  the  front  cell  and  the  rotary  prism  stands  at  seven 
degrees,  the  prism-degree  measurement  of  the  esotropia 
is  thirty-two  degrees,  one-half  of  which  would  give  the 
degrees  of  arc — viz.,  sixteen  degrees.  As  already  stated, 
the  angle  gamma  does  not  have  to  be  considered  in  con- 
nection with  the  phorometer  measurement.  It  would  be 
very  difficult  to  take  the  measurement  of  esotropia  with 
the  prisms  of  the  refraction  case  held  by  the  hands  of 
the  operator.  Though  this  would  be  tiresome  and  tedi- 
ous, it,  nevertheless,  would  be  accurate. 

MEASUREMENT  BY  THE  PERIMETER. — Have  the  head 
placed  as  if  the  purpose  were  to  take  the  field  of  the 
non-deviating  eye,  which  should  be  made  to  fix  the  point 
in  the  center  of  the  semicircle.  A  candle  or  small  elec- 
tric light  should  be  moved  along  that  arc  toward  which 
the  deviating  eye  points,  and  it  should  be  stopped  the 
moment  that  the  image  reflected  from  the  center  of  the 
cornea,  the  light,  and  the  eye  of  the  observer  are  in  line. 
The  number  on  the  perimeter  arm,  at  the  point  where 
the  light  was  stopped,  gives  the  measurement  of  the 
deviation  in  arc  degrees.  If  the  esotropia  thus  meas- 
ured should  appear  to  be  twenty-five  degrees,  it  will  be 
more  if  the  angle  gamma  is  temporal,  or  less  if  this 
angle  is  nasal.  The  next  step  is  to  determine  the  pres- 


532  ESOTROPIA. 

ence  or  absence  of  the  angle  g-amma,  and,  if  present,  its 
size.  To  do  this,  the  good  eye  must  be  covered  while 
the  patient  fixes,  with  the  esotropic  e}re,  the  point  in  the 
center  of  the  perimeter  arc.  When  the  candle  is  held 
immediately  behind  this  point,  if  the  image  is  reflected 
from  the  center  of  the  cornea  so  that  the  image,  the 
light,  and  the  eye  of  the  observer  are  in  line,  there  is  no 
angle  g-amma,  and,  therefore,  nothing  is  to  be  taken 
from  nor  added  to  the  measurement  of  the  esotropia; 
but  if  the  light  must  be  moved  in  the  temporal  arc  for 
the  image,  the  light,  and  the  eye  of  the  observer  to  be 
in  line,  there  is  an  angle  gramma,  the  size  of  which  is 
shown  by  the  number  at  the  point  on  the  perimeter  arm 
at  which  the  light  was  stopped  when  the  image  appeared 
reflected  from  the  center  of  the  corneal  surface.  The 
angle  thus  formed  being  temporal,  it  should  be  added  to 
the  measurement  of  the  apparent  esotropia,  in  order  to 
show  the  quantity  of  the  real  deviation;  but  if,  in  find- 
ing the  angle  g~amma,  the  light  has  been  moved  into  the 
nasal  arc,  the  angle  would  be  nasal,  and  should  be  sub- 
tracted from  the  measurement  of  the  apparent  esotropia, 
in  order  to  show  the  quantity  of  the  actual  deviation. 
If  the  perimeter  is  carefully  used  in  the  manner  set 
forth,  the  results  must  be  correct.  It  is  applicable  to 
all  cases  of  esotropia  in  which  the  deviating  eye  can  be 
made  to  fix  when  the  good  eye  is  covered;  while  the 


ESOTROPIA.  533 

phorometer  method  can  be  used  only  in  those  cases  in 
which,  by  means  of  a  red  glass  before  the  good  eye,  con- 
sciousness of  diplopia  can  be  awakened. 

When  the  squinting1  eye  cannot  see,  therefore  cannot 
fix,  the  angle  g-amma  cannot  be  measured,  and  for  this 
reason  it  cannot  be  taken  from  nor  added  to  the  perimeter 
measurement  of  the  esotropia. 

THE  TAPE  MEASUREMENT. — Priestly  Smith's  method 
of  measuring  esotropia  is  easy  and  fairly  accurate.  By 
this  method  the  angle  g-amma  is  not  considered.  To 
make  this  test,  one  must  have  an  ophthalmoscope;  two 
tape  lines,  each  one  meter  long-;  and  a  candle,  a  lamp,  or 
a  gas  jet.  The  tape  lines,  at  one  end,  should  be  fas- 
tened to  a  ring  large  enough  to  allow  the  handle  of  the 
ophthalmoscope  to  pass  through  it,  while  the  other  two 
ends  should  be  free,  and  on  one  tape  should  be  a  scale 
indicating  arc  degrees.  With  the  light  above  and  be- 
hind the  patient,  the  operator  seats  himself  one  meter  in 
front  of  him.  He  gives  to  the  patient  the  free  end  of 
the  unmarked  meter  tape,  and  tells  him  to  place  it  im- 
mediately beneath  his  good  eye;  and  then,  with  the  oph- 
thalmoscope in  front  of  his  own  eye  which  corresponds 
with  the  patient's  non-deviating  eye — that  is,  his  right 
eye,  if  it  is  the  patient's  left  eye  that  turns  in — he  with- 
draws from  the  patient  as  far  as  the  tape  will  allow 
whose  ring  end  is  fastened  to  the  ophthalmoscope,  or  to 


534  ESOTROPIA. 

the  thumb  of  the  hand  holding-  the  ophthalmoscope.  He 
directs  the  patient  to  fix  the  hole  in  the  mirror  while  he 
reflects  the  light  into  the  fixing-  eye.  If  there  is  no 
angle  gamma,  the  operator  sees  the  image  of  the  blaze 
reflected  from  the  center  of  this  cornea;  but  on  reflect- 
ing the  light  into  the  deviating  eye,  while  the  good  eye 
still  fixes  the  hole  in  the  mirror,  the  image  of  the  blaze 
will  be  seen  toward  the  temporal  margin  of  this  cornea, 
the  distance  from  the  center  corresponding  to  the  amount 
of  the  esotropia.  The  operator  now  takes  the  marked 
meter  tape  in  his  free  hand  (he  holds  the  mirror  before 
his  right  eye  with  his  left  hand,  and  vice  versa)  close  to 
its  attachment  to  the  ring,  and,  slowly  extending  it  at 
right  angles  to  the  other  tape,  he  directs  the  patient  to 
look  at  his  moving  thumb  with  his  good  eye.  Through- 
out this  step  in  the  test,  the  light  from  the  mirror  is 
kept  on  the  cornea  of  the  deviating  eye,  and  the  operator 
watches  the  reflected  image  as  it  approaches  the  center 
of  the  cornea.  The  moment  the  image  is  seen  at  the 
center  of  the  cornea  the  operator  stops  the  movement  of 
his  hand,  and  immediately  reads  on  the  scale  the  number 
of  degrees  the  good  eye  had  to  move  toward  the  nose 
in  order  that  the  deviating  eye  might  become  straight. 
Since  the  two  eyes  moved  comitantly,  the  reading  on  the 
scale  is  the  measurement  of  the  esotropia.  This  method 
is  not  as  accurate  as  either  the  phorometer  or  the  perim- 


ESOTROPIA.  535 

euer  methods,  for  the  reason  that  one  cannot  be  certain 
that  the  marked  tape  is  at  right  angles  to  the  unmarked 
tape. 

LINEAR  MEASUREMENT  — 1/awrence 's  strabismome- 
ter,  which  is  the  best  means  for  taking  the  linear  meas- 
urement of  squint,  is  rapid,  but  not  accurate,  in  its  work. 
The  lid  piece  is  concave  on  one  side  so  as  to  rest  evenly 
against  the  lower  lid;  on  the  convex  side  it  is  graduated 
in  millimeters  in  both  directions  from  the  central  point, 
which  is  marked  zero.  In  making  the  test,  the  operator 
covers  the  good  eye,  thus  forcing  the  patient  to  fix  some 
distant  object,  immediately  in  front,  with  the  deviating 
eye.  The  instrument  is  now  placed  in  contact  with  the 
lower  lid  of  the  now-fixing  eye,  so  that  the  point  marked 
zero  may  be  directly  in  line  with  the  center  of  the  pupil. 
On  uncovering  the  good  eye,  it  at  once  fixes  the  test  ob- 
ject, while  the  deviating  eye  turns  toward  the  nose.  The 
extent  of  the  turning  in  millimeters  is  shown  by  that 
mark  on  the  scale  that  falls  immediately  beneath  the 
center  of  the  pupil. 

HIRSCHBERG'S  METHOD. — By  this  method  accuracy 
cannot  be  attained.  The  test  object  is  a  candle  held 
twelve  inches  from  the  patient,  and  immediately  before 
him  on  a  level  with  his  eyes.  With  both  eyes  uncovered 
he  is  directed  to  look  at  the  candle.  The  image  of  the 
candle  is  reflected  from  the  corneal  center  of  the  fixing 


536  ESOTROPIA. 

eye,  but  from  the  temporal  side  of  the  cornea  of  the 
esotropic  eye  Hirschberg  estimates  that  the  deviation 
is  ten  degrees  or  less,  if  the  reflected  image  is  nearer  the 
center  than  the  margin  of  the  pupillary  area;  from  twelve 
degrees  to  fifteen  degrees,  if  the  image  is  at  the  margin 
of  the  pupil;  twenty-five  degrees,  if  the  image  is  halfway 
between  the  center  of  the  cornea  and  its  margin;  from  for- 
ty-five degrees  to  fifty  degrees,  if  the  image  is  at  the  cor- 
neal  margin.  Esotropic  cases  were  divided  by  Hirsch- 
berg' into  these  several  groups  that  he  might  determine 
the  kind  of  operations  to  be  done  in  any  individual  case. 
Since  complete  tenotomies  ought  never  to  be  performed 
on  esotropes,  the  Hirschberg  method  of  testing*  is  of  no 

use. 

SYMPTOMS  OP  COMITANT  ESOTROPIA. 

There  is  no  nervous  tension  of  the  externus  of  the  eso- 
tropic eye,  for  the  position  assumed  by  this  eye  is  that  of 
equilibrium  of  all  the  recti  and  the  oblique  muscles. 
The  tension  of  the  externus  of  the  fixing  eye  may  be 
lessened,  if  not  relieved,  by  a  turning  of  the  face  toward 
the  corresponding  side,  so  as  to  let  the  visual  axis  cross 
the  extended  median  plane  of  the  head  between  the  eye 
and  the  object  of  fixation.  Headache  or  other  symp- 
toms, in  these  cases,  usually  attributed  to  eye-strain, 
depend  largely  on  the  abnormal  tension  of  the  externus 
of  the  fixing  eye,  though  this  is  sometimes  relieved  by 


ESOTROPIA.  537 

an  acquired  side-pose  of  the  head.  But  in  some  of  these 
cases  it  may  depend  on  the  nervous  tension  of  the  ciliary 
muscle  in  its  effort  to  correct  the  hyperopia  or  hyperopic 
astigmatism  of  the  fixing  eye,  together  with  the  asso- 
ciated tension  of  the  ciliary  muscle  of  the  non-fixing  eye; 
or  it  may  result  from  the  effort  of  the  obliques  to  par- 
allel the  vertical  axis  of  the  fixing  eye  with  the  median 
plane  of  the  head. 

AMBL,YOPIA. — The  one  subjective  symptom  common 
to  most  cases  of  permanent  esotropia,  and  that  may  ex- 
ist unnoticed  for  many  years,  is  amblyopia  of  the  non- 
fixing  eye.  While  in  some  cases  this  may  be  congenital, 
in  most  cases  it  is  acquired.  The  blindness  is  in  the 
mind,  and  not  in  the  eye.  Nature  has  provided  only  two 
methods  by  either  one  of  which  a  person  may  be  freed 
from  the  annoyance  of  seeing  everything  double:  First, 
the  proper  regulation  of  the  visual  axes  by  the  recti 
muscles,  so  that  they  may  always  be  in  the  same  plane 
and  converged  at  the  point  of  view,  and  the  paralleling 
of  the  vertical  axes  of  the  eyes  with  the  median  plane 
of  the  head,  thus  making  binocular  single  vision  possible; 
second,  in  the  absence  of  any  one  or  all  three  of  the  con- 
ditions essential  to  binocular  single  vision,  then  mental 
suppression  of  the  images  in  one  eye.  The  habit  of 
mental  suppression  cannot  be  established,  except  in  in- 
fancy and  early  childhood.  Once  this  habit  is  estab- 


538  ESOTROPIA. 

lished,  it  is  hard  to  break  at  any  period  of  life;  but  the 
task  can  be  more  easily  accomplished  early  in  life  than 
in  later  years.  In  all  cases  it  is  probable  that  the  am- 
blyopic  eye  would  become  useful,  if  accident  or  disease 
should  destroy  the  fellow  eye.  W.  B.  Johnson,  of  Pat- 
erson,  N.  J.,  has  observed  and  reported  two  such  cases. 
His  report  has  done  much  to  prove  that  amblyopia  ex 
anopsia  is  not  a  myth.  Faithful  exercise  of  the  little 
visual  power  of  the  amblyopic  eye,  by  covering-  the  good 
eye,  will  greatly  improve  its  vision,  especially  in  young- 
persons.  Without  this  special  exercise  it  has  often  been 
noticed  that  vision  improved  in  the  formerly  non-fixing 
eye  after  the  muscles  had  been  readjusted  so  as  to 
properly  regulate  the  visual  axes  and  the  vertical  axes. 
There  is  now  but  little  room  for  doubting  that  the  am- 
blyopia of  esotropia  is  mental,  and  not  ocular. 

The  chief  objective  symptom  is  disfigurement.  How- 
ever beautiful  a  young  lady  may  be  otherwise,  if  her 
eyes  are  crossed  that  beauty  is  marred;  and  if  she  is  oth- 
erwise unprepossessing,  crossed  eyes  could  but  render  her 
more  so.  A  young  man  afflicted  with  esotropia  cannot 
be  so  handsome  as  he  would  be  if  his  eyes  were  straight. 
A  girl  or  boy,  a  woman  or  man  with  esotropia  is  at  a  de- 
cided disadvantage  from  a  cosmetic  point  of  view;  and  if 
there  was  no  other  reason  for  operating,  this  one  would 
be  sufficient. 


ESOTROPIA.  539 

An  objective  symptom  that  should  never  be  neglected 
in  the  study  of  any  case  of  esotropia  is  the  turning*  in  of 
the  good  eye  when  under  the  cover,  at  which  time  the 
fellow  eye  must  become  the  fixing  eye.  The  secondary 
esotropia  should  be  equal  to  the  primary;  but  if  the 
secondary  esotropia  is  greater  than  the  primary,  it 
points  to  paretic,  and  not  to  comitant,  esotropia. 

COMPLICATIONS  OF  ESOTROPIA. — These  are  errors 
of  refraction;  hypertropia,  single  or  double;  catatropia, 
single  or  double;  hypertropia  of  one  eye  and  catatropia 
of  the  other;  and  cyclotropia,  either  plus  or  minus.  Hy- 
pertropia, catatropia,  and  cyclotropia  will  be  studied 
farther  on  in  this  chapter.  Here  it  may  be  said  that 
these  errors,  if  unassociated  with  esotropia,  would  often 
be  phorias,  and  not  tropias.  Nevertheless,  before  operat- 
ing for  esotropia,  it  is  important  to  know  if  these  errors 
exist;  it  is  also  important,  before  operating  for  esotro- 
pia, to  study  well  the  refraction  of  the  two  eyes,  and  to 
correct  those  errors  (hyperopia  and  hyperopic  astig- 
matism) that  are  not  only  complications  of  esotropia, 
but  act  as  causes  also.  Another  condition  which  com- 
plicates esotropia  is  amblyopia,  which  is  also  a  result  of 
esotropia. 

TREATMENT  OF  ESOTROPIA. 

Hyperopia  and  hyperopic  astigmatism,  often  a  compli- 
cation of  esotropia,  are  just  as  often  causative  of  this 


540  ESOTROPIA. 

condition.  A  very  few  cases  of  esotropia  have,  for  their 
chief  causes,  these  errors  of  refraction.  It  is  only  a  case 
of  this  kind  that  eventually  recovers  spontaneously;  but 
spontaneous  recoveries  are  rare.  Nor  should  these  cases 
be  allowed  to  wait  for  such  a  recovery,  which  would  be 
years  in  coming-;  but  they  should  be  cured  at  the  earliest 
possible  moment.  The  only  treatment  needed  for  such 
cases  is  the  full  correction  of  the  hyperopic  error,  and  at 
the  earliest  time  possible.  Such  a  patient,  if  only  two 
years  old,  will  wear  the  correcting"  lenses  kindly,  because 
of  the  relief  experienced.  If  the  spectacles  are  not  given 
to  the  little  fellow  promptly  after  his  morning  toilet,  he 
will  call  for  them.  It  is  often  interesting-  to  experiment 
with  such  a  case  by  having  him  look  at  some  distant  ob- 
ject one  moment  through  the  lenses,  when  the  eyes  will 
be  straight,  and  then  a  moment  without  the  lenses,  when 
the  eyes  will  cross.  The  repeated  raising  and  lowering 
of  the  lenses  will  show  alternate  crossing  and  straight- 
ness.  One  who  has  seen  these  changes  cannot  reasonably 
doubt  the  effectiveness  of  convex  lenses  in  the  treatment 
of  esotropia. 

There  are  two  reasons  for  the  early  adjustment  of 
convex  lenses  in  the  treatment  of  esotropia.  One  is  that 
it  is  in  the  earliest  years  of  life  that  the  power  of  mental 
suppression  of  images  in  the  deviating  eye  is  acquired. 
To  prevent  this  amblyopia  is  to  cure  the  esotropia;  or, 


ESOTROPIA.  541 

if  the  habit  of  suppression  has  already  been  formed,  the 
early  correction  of  the  esotropia  gives  the  patient  a 
chance  to  recover  the  lost  vision  with  greater  ease  than 
would  be  possible  in  later  years.  The  other  reason  for 
the  early  correction  of  the  hyperopic  error  that  has 
caused  the  esotropia  is  the  relief  the  lenses  give  to  the 
brain-center  that  supplies  power  to  the  ciliary  muscles. 
With  the  convex  lenses  on,  this  brain-center  is  no  longer 
over-stimulated,  and  consequently  the  third  conjugate 
center  is  no  longer  over-excited.  The  extra  nerve  force 
that  must  be  expended  by  these  centers,  if  the  hyperopic 
error  remains  uncorrected,  must  be  at  the  expense  of 
nerve  force  needed  by  other  centers. 

Every  little  child  whose  eyes  are  crossed  should  be 
given  the  chance  of  a  cure  by  means  of  spectacles.  If 
the  hyperopic  error  is  the  whole  cause  of  the  esotropia, 
the  lenses  will  certainly  effect  a  speedy  cure;  if  the  hy- 
peropia  is  only  one  factor,  while  esophoria  is  the  other 
factor,  in  the  production  of  esotropia,  the  early  correc- 
tion of  the  focal  error  will  often  make  it  impossible  for 
the  esophoria  to  continue  to  transform  itself  into  esotro- 
pia. The  eyes  can  be  straightened,  in  some  of  these  cases, 
by  means  of  convex  lenses,  but  the  esophoria  will  remain. 
Later,  because  of  nervous  symptoms,  the  esophoria  may 
demand  treatment,  either  surgical  or  non-surgical.  To 
do  any  kind  of  surgery  for  the  cure  of  an  esotropia  that 


542  ESOTROPIA, 

has  for  its  sole  cause  a  hyperopic  error  must  result  in 
harm.  In  early  life  no  case  of  esotropia  that  is  hyper- 
opic should  be  subjected  to  operation  until  it  becomes  ev- 
ident that  convex  lenses  cannot  straighten  the  eyes,.  It 
is  doubtful  if  the  almost  universal  practice  of  keeping- 
such  eyes  under  the  influence  of  atropine  is  helpful,  but 
certainly  both  eyes  should  be  under  the  influence  of  either 
atropine  or  homatropine  at  the  time  the  measurements 
are  taken,  and  the  full  error  thus  found  should  be  cor- 
rected. Worth  is  correct  in  his  advocacy  of  atropine  in 
the  good  eye  only  after  the  convex  lenses  have  been  giv- 
en, and  the  reason  for  this  is  not  far  away:  it  allows  the 
child  to  use  the  better  eye  for  distance,  but  forces  him 
to  use  the  deviating  eye  for  near  objects — a  very  good 
way  for  curing  the  amblyopia.  For  the  same  reason 
atropine  could  be  used  in  the  good  eye  when  there  is  any 
other  form  of  heterotropia. 

If  in  a  month  or  two  convex  lenses  do  not  cause  the 
eyes  to  swing  straight,  surgery  should  be  resorted  to, 
however  young  may  be  the  patient.  By  "surgery"  is 
meant  the  right  kind  of  surgery — partial  tenotomies  of 
the  interni,  with  or  without  shortenings  of  the  externi. 
A  complete  tenotomy  in  the  case  of  a  child  should  never 
be  done,  and  advancements  should  be  avoided.  Very 
slight  operations,  if  done  in  early  life,  will  accomplish 
as  much  as  more  extensive  operations  done  in  later  years; 


ESOTROPIA.  543 

but  an  esotrope  never  grows  sufficiently  old  to  justify 
complete  tenotomies. 

If  the  refraction  of  the  eyes  is  myopic,  this  error  can- 
not have  been  a  factor  in  the  production  of  the  esotropia; 
hence  the  correcting1  lenses  cannot  aid  in  the  cure.  Sur- 
gery alone  can  bring1  these  eyes  straight.  Such  a  case  of 
esotropia  can  never  recover  spontaneously.  An  esotrope 
who  is  emmetropic  can  be  cured  only  by  surgery.  Atro- 
pine  used  in  the  good  eye  will  help  after  surgery  has 
been  resorted  to. 

Esotropic  patients  who  have  been  allowed  to  go  for 
years  without  treatment,  whatever  may  have  been  the 
cause  or  causes,  become  more  or  less  amblyopic  in  the 
deviating1  eye.  In  many  of  these  cases  the  correction  of 
the  hyperopia,  if  it  had  been  given  early,  would  have 
speedily  straightened  the  eyes;  but  if  this  correction  is 
withheld  until  the  suppression  habit  has  become  estab- 
lished, the  cure,  if  it  can  ever  be  effected  by  the  convex 
lenses,  is  much  more  tedious.  Nevertheless,  a  fair  trial 
of  the  lenses  should  be  given,  a  great  aid  to  which  will 
be  the  forced  use  of  the  deviating- — amblyopic — eye,  for 
a  short  while,  several  times  a  da}7.  This  is  done  b}T 
placing-  a  flap  before  the  g-ood  eye,  thus  compelling  the 
mind  to  receive  the  impression  of  the  images  on  the  ret- 
ina of  the  bad  eye.  At  such  time,  and  at  all  times,  the 
correcting  lenses  should  be  worn.  At  first  only  large 


544  ESOTROPIA. 

objects  in  the  distance  should  be  observed;  later,  pic- 
tures or  large  print  should  be  looked  at.  If  the  pa- 
tient is  old  enough,  he  will  observe  the  improved  state 
of  his  vision  from  week  to  week,  and  will  thus  be  en- 
couraged to  continue;  if  the  patient  is  a  child,  the  exer- 
cise should  be  enforced,  for  the  little  one  cannot  appre- 
ciate the  results.  This  practice  at  first  may  be  con- 
tinued only  a  few  minutes — from  ten  to  thirty;  later,  it 
should  be  prolonged  for  an  hour  or  more;  and,  in  either 
case,  it  should  be  repeated  two  or  more  times  daily. 
The  training  of  the  mind  to  use  the  amblyopic  eye  is  the 
best  means  for  the  beginning  of  the  development  of  the 
fusion  power.  Whether  a  child  or  a  grown  person,  the 
use  of  atropine  in  the  good  eye  will  help  to  train  the  mind 
to  use  the  bad  eye. 

This  training  of  the  mind  to  use  the  amblyopic  eye  is 
necessary  even  in  those  cases  that  must  be  subjected  to 
operations,  else  binocular  single  vision  may  not  be  ob- 
tained. The  chief  object  in  view  in  the  treatment  of 
esotropia,  whether  by  lenses  or  by  operations,  or  by 
both,  is  the  establishment  of  binocular  single  vision. 
There  should  be  fewer  failures  in  this  direction  in  the 
future  than  in  the  past.  The  forced  use  of  the  ambly- 
opic eye  will  make  success  more  certain. 

After  a  few  months  of  training,  as  set  forth  above, 
the  stereoscope  can  be  brought  into  use.  At  first  the 


ESOTROPIA.  545 

two  pictures  used  should  be  unlike,  but  of  such  a  nature 
as  to  be  easily  combined.  The  best  example  is  the  pic- 
ture of  a  bird  before  one  eye  and  the  picture  of  a  cage 
before  the  other.  The  bird,  at  first  outside  the  cage,  will 
be  observed  by  the  child  to  approach  and  enter  it,  finally 
resting1  on  the  perch.  Other  pictures  that  can  be  asso- 
ciated should  be  provided.  Later,  cards  may  be  used, 
on  one  end  of  which  is  drawn  one  part  of  an  object;  on 
the  other  end,  the  remaining-  part  of  the  object.  If  the 
complete  object  is  seen,  the  retinal  images  have  been 
fused.  Later,  the  pictures  ordinarily  used  in  the  stereo- 
scope may  be  given.  To  be  certain  that  these  pictures 
have  been  fused,  it  becomes  necessary  to  make  some 
change  in  each  at  different  parts;  for  example,  cut  off 
the  upper  left-hand  corner  of  one  picture  and  the  lower 
right-hand  corner  of  the  other.  If  an  unmutilated  pic- 
ture is  seen,  the  two  retinal  images  have  been  fused. 
Many  other  changes,  such  as  placing  different  kinds  of 
marks  on  the  pictures,  would  readily  suggest  them- 
selves. When  the  esotropia  is  of  high  degree,  training 
by  means  of  the  ordinary  stereoscope  is  impossible. 

The  best  means  for  training  the  fusion  power  is,  prob- 
ably, the  Worth  reflecting  stereoscope,  or  amblyoscope, 
shown  in  Fig.  75.  This  instrument  can  be  used  in  any 
and  all  cases  of  esotropia;  but  before  undertaking  the 
training  of  the  fusion  faculty  by  this  means,  the  ambly- 


546 


ESOTROPIA. 


opia  of  the  deviating  eye  should  be  treated  in  the  manner 
already  set  forth.  As  shown  in  the  cut,  the  Worth  in- 
strument consists  of  two  symmetrical  halves;  each  half 
is  made  by  uniting-  two  tubes,  a  long  and  a  short  one,  at 
an  angle  of  one  hundred  and  twenty  degrees,  and  the 
two  halves  are  joined  by  the  hinge  shown  at  A.  These 


halves  are  further  connected  by  the  brass  arc  D-K-F,  in 
which  are  two  slots,  and  by  means  of  which  the  distal 
ends  of  the  tubes  may  be  made  to  vary  the  distance  be- 
tween them.  At  D  and  F  are  binding  screws  for  "fix- 
ing" the  proper  relationship  of  the  tubes,  when  it  has 
been  attained,  for  any  given  pair  of  esotropic  eyes.  By 


ESOTROPIA.  547 

placing1  the  binding*  screws  at  the  inner  ends  of  their  re- 
spective slots  the  instrument  is  in  adjustment  for  sixty 
degrees  of  esotropia,  and  by  moving-  these  screws  to  the 
outer  ends  of  their  respective  slots  the  instrument  will 
be  in  adjustment  for  thirty  degrees  of  exotropia. 

At  G-H  of  each  tube  there  is  an  arrangement  for  the 
insertion  of  translucent  picture  slides.  At  A-X  of  each 
tube  there  is  an  oval  mirror.  At  the  ocular  ends  A-B 
there  are  lenses  of  a  certain  power,  which  may  be  sup- 
plemented by  other  lenses  that  may  be  needed  by  any 
individual  case,  for  making  sharp  the  outline  of  the  im- 
ages reflected  from  the  mirrors. 

In  using  this  instrument  for  training  the  fusion  facul- 
ty, images  that  differ,  and  yet  can  be  associated,  should 
be  placed  in  the  distal  ends  of  the  tubes.  The  best  ex- 
ample is  the  picture  of  a  cage  for  one  tube,-  and  that  of 
a  bird  for  the  other.  The  tubes  must  be  related  corre- 
sponding to  the  degree  of  deviation  of  the  esotropic  eye, 
so  that  the  reflected  image  of  the  one  picture  may  fall  on 
one  macula,  while  that  of  the  other  falls  on  the  other 
macula.  At  first  the  patient  may  see  only  the  cage,  and 
not  the  bird,  or  vice  versa.  By  increasing,  relatively 
the  intensity  of  the  light  entering  the  tube  that  is  before 
the  squinting  eye,  the  bird  is  finally  seen  in  the  cage. 
Any  two  pictures  that  can  be  associated  may  be  used, 
but  none  can  be  better  than  those  of  the  bird  and  the 


548  ESOTROPIA. 

cage.  Later,  one  may  place  in  the  tubes  pictures  that 
represent  different  parts  of  an  object,  the  fusion  of  the 
two  making-  the  thing-  represented  in  parts  appear  as 
a  whole.  A  very  great  variety  of  such  pictures  should 
be  on  hand,  so  as  to  make  the  exercise  interesting-  to  the 
little  patient. 

These  exercises  should  not  be  undertaken  until  treat- 
ment has  relieved,  to  a  considerable  extent,  the  ambly- 
opia  of  the  deviating  eye.  It  would  be  well  if  the  fusion 
faculty  could  be  trained  before  operating,  if  circumstances 
will  allow,  and  certainly  before  the  final  operations  are 
done,  if  the  best  results  are  to  be  expected. 

BAR-READING. — Perhaps  one  of  the  best  means  for 
perfecting  the  fusion  faculty  is  bar-reading.  A  strip  of 
card-board,  half  an  inch  wide — or  even  a  pencil,  though 
this  is  hardly  wide  enough — should  be  held  between  the 
eyes  and  the  printed  page,  about  four  inches  from  the 
latter.  This  will  obscure  some  of  the  words  for  each 
eye,  and  will  thus  interfere  with  the  reading,  unless  both 
eyes  are  being  used.  The  words  obscured  for  one  eye 
are  seen  by  the  other,  in  binocular  vision;  therefore  the 
bar  does  not  hinder  the  reading;  and,  since  this  is  so, 
the  bar-reading  exercise  may  be  continued  for  hours  at  a 
time.  There  can  be  no  question  as  to  its  value. 

Treatment  of  the  amblyopia  is  by  excluding  the  good 
eye,  by  the  adjustment  of  lenses  that  correct  hyperopic 


ESOTROPIA.  549 

errors;  by  the  use  of  atropine  in  the  good  eye,  forcing 
the  near  use  of  the  other;  by  the  training  of  the  fusion 
faculty  with  the  simple  stereoscope  or  the  reflecting  ster- 
eoscope, and,  later,  by  bar-reading — these  are  non-opera- 
tive means  that  should  be  applied  to  all  cases  of  esotro- 
pia,  even  to  those  that  must  be  subjected  to  operations. 

OPERATIVE  TREATMENT  OF  ESOTROPIA. 

If  all  cases  of  esotropia  could  be  treated  at  the  earliest 
possible  time  —  that  is,  when  the  condition  first  shows 
itself  —  probably  not  more  than  twent}^-five  per  cent  of 
them  could  be  cured  by  non-operative  means.  Of  this 
twenty-five  per  cent,  a  fair  proportion  would  require, 
later  in  life,  operations  for  the  relief  of  the  esophoria, 
which  had  been  one  of  the  causes,  probably  the  chief 
cause,  of  the  esotropia.  A  cure  of  esotropia,  in  the 
strictest  sense,  would  mean  that  every  causative  factor 
has  been  removed.  Convex  lenses,  given  for  the  correc- 
tion of  hyperopic  errors,  remove  only  one  factor;  but  in 
doing  this  much,  they  sometimes  render  inoperative  the 
esophoric  factor.  However,  the  latter  can  be  removed 
only  by  exercise  or  by  operations. 

It  cannot  be  emphasized  too  strongly  that  complete 
tenotomies  are  not  indicated  in  esotropia,  even  though 
the  error  should  be  high  in  degree;  and  if  complete  te- 
notomies should  not  be  done,  it  goes  without  the  saying 


550  ESOTROPIA. 

that  the  "check  ligaments,"  so-called,  should  never  be 
severed.  It  must  be  granted  that  some  cases  on  whom 
complete  tenotomies  have  been  done  have  resulted  in  a 
cure  of  the  esotropia,  but  it  must  be  conceded  also  that 
a  greater  number  have  not  been  cured.  One  does  not 
have  to  theorize  as  to  the  possibility  of  an  esotropia's  be- 
ing- converted  into  an  exotropia  by  complete  tenotomies  of 
the  interni,  for  this  unfortunate  result  has  been  observed 
in  a  multitude  of  cases.  In  every  complete  tenotomy  the 
control  that  comes  from  anchorag-e  is  lost.  Uncut  fibers 
of  the  tendon  constitute  the  best  anchorage;  but  if  by 
accident  all  the  fibers  of  a  tendon  should  be  cut,  the 
divided  tendon  should  be  anchored  to  the  globe  by  means 
of  a  stitch.  Otherwise,  the  dang-er  is  great  that  the 
muscle  may  retract  too  far,  and  thus  become  a  crippled 
muscle. 

The  only  complete  tenotomy  that  can  be  said  to  be  at 
all  safe  is  that  advised  by  Panas.  In  this  operation  the 
hook  is  passed  beneath  the  tendon  (of  the  internus  in  eso- 
tropia), and  by  it  the  eye  is  rotated  outward  until  the  cor- 
nea is  almost  hidden  behind  the  external  canthus.  This 
done,  the  force  is  relaxed  and  the  tendon  is  completely 
divided.  The  element  of  safety  lies  in  the  fact  that  the 
over-stretched  muscle  has  been  rendered  paretic,  and, 
therefore,  does  not  retract  so  far  as  it  otherwise  would 
do.  The  cut  tendon  becomes  adherent  to  the  globe  be- 


ESOTROPIA.  551 

fore  the  muscle  recovers  from  its  paresis;  hence  its  new 
attachment  is  as  favorable  for  normal  action  of  the  mus- 
cle as  it  is  possible  for  it  to  be  after  a  complete  tenot- 
omy.  The  element  of  safety  in  the  Panas  operation  is 
not  sufficient  to  justify  its  adoption,  in  the  face  of  the 
fact  that  there  are  safer  operative  means  for  the  treat- 
ment of  esotropia. 

If  advancements  are  done  in  connection  with  complete 
tenotomies,  the  latter  become  even  more  hazardous. 

Landolt's  method  of  treating1  esotropia  by  advance- 
ments of  the  externi  alone  is  much  to  be  preferred  to 
complete  tenotomies  of  the  interni;  for  it  is  not  attended 
by  the  danger  of  converting1  an  esotropia  into  an  exotro- 
pia,  and  it  offers  a  better  chance  for  the  giving*  of  binoc- 
ular single  vision  in  all  parts  of  the  field. 

As  in  all  other  matters,  so  in  operating  for  esotropia, 
extremes  should  be  avoided.  "The  golden  mean"  is 
not  an  inapt  expression.  One  extreme  in  the  treatment 
of  esotropia  is  complete  tenotomies  of  the  interni  and  the 
cutting  of  the  check  ligaments,  "without  shortenings  or 
advancements  of  the  externi;  the  other  extreme  is  ad- 
vancements of  the  externi,  without  interfering  in  any  way 
with  the  interni. 

By  the  one  method  the  strong  muscles  are  made  weak 
by  setting  them  back  (and,  as  already  shown,  the  danger 
lies  in  the  probability  that  they  will  be  set  back  too  far) ; 


552  ESOTROPIA. 

by  the  other  method  the  weak  muscles  are  made  strong 
by  bringing1  their  attachments  farther  forward,  with  but 
little  danger  of  bringing  them  too  far.  If  enough  could 
be  accomplished  by  the  advancements,  in  all  cases,  it 
would  be  almost  the  ideal  operation. 

The  ideal  operation  for  the  cure  of  esotropia  and  its 
complications  consists  of  advancements  of  both  externi, 
or,  if  in  young1  children,  shortening's  of  both  externi,  to 
make  them  stronger,  and  partial  tenotomies  of  both  in- 
terni  to  make  them  weaker.  The  object  in  view  is  to 
bring  the  strength  of  the  externi  up  to  the  normal  both 
as  to  abduction  and  abversion,  and  to  reduce  the  strength 
of  the  internt  only  to  the  normal  both  as  to  adduction 
and  adversion.  There  is  practically  no  danger  of  over- 
reaching the  limit  in  either  of  the  two  directions. 

There  are  a  few  cases  of  esotropia,  as  will  be  shown 
farther  on,  in  which  it  would  not  be  correct  to  do  any- 
thing primarily  but  advance  the  externi  and  depress  their 
planes  of  rotation. 

The  two  effects  that  can  be  accomplished  by  advance- 
ments are  an  increase  of  tension  and  a  change  of  the 
plane  of  rotation.  The  former  must  always  be  accom- 
plished, while  the  latter  should  be  accomplished  in  some 
cases,  but  avoided  in  others.  The  two  effects  that  can 
be  accomplished  by  partial  tenotomies  are  diminution  of 
tension  and  a  change  of  the  plane  of  rotation.  The 


ESOTKOPIA.  553 

former  must  always  be  attained,  while  the  latter  must 
be  accomplished  in  some  cases,  but  avoided  in  others. 

Before  operating  on  any  case  of  esotropia  it  must  be 
decided  whether  the  tension  alone  shall  be  altered,  or 
whether,  in  connection  with  altering1  the  tension,  the 
plane  of  rotation  shall  be  changed.  To  alter  only  the 
tension  of  the  muscles,  when  their  planes  also  should  be 
changed,  would  be  to  fail  to  cure  the  case.  In  all  cases 
in  which  the  deviating  eye  is  not  totally  blind  it  may  be 
known  beforehand  just  what  kind  of  an  operation  should 
be  done.  If  the  deviating  eye  is  totally  blind,  there  can 
be  no  indication  for  a  change  of  plane,  and  all  that 
should  be  done  for  such  a  case  would  be  to  alter  the 
tension.  * 

The  operative  treatment  of  uncomplicated  esotropis 
should  be  applied  primarily  to  the  deviating  eye,  with 
the  view  of  leaving  some  of  the  error  to  be  corrected  by 
means  of  operations  on  the  other  eye.  The  externus  of 
the  deviating  eye  should  be  well  advanced,  straight-for- 
ward, so  as  to  increase  its  tension  without  changing  its 
plane  of  rotation,  and  at  the  same  time  a  central  partial 
tenotomy  of  the  opposing  internus  should  be  done,  the 
operator  always  being  careful  to  leave  uncut  a  sufficient 
number  of  fibers  above  and  below  to  act  as  stay-cords. 
By  this  partial  tenotomy  the  tension  is  reduced,  but  the 
plane  is  not  changed.  These  two  operations,  done  at  the 


554  ESOTROPIA. 

same  time,  will  usually  enable  the  patient  to  fix  with  this 
eye,  the  other  eye  now  becoming  slightly  crossed. 

After  an  interval  of  two  or  more  weeks  a  central  par- 
tial tenotomy  of  the  internus  of  the  good  eye  should  be 
done,  with  the  view  of  lessening  its  tension  without 
changing  its  plane.  If  it  appears  that  the  effect  of  this 
partial  tenotomy  is  not  enough,  the  externus  of  this  eye 
should  be  shortened,  straight-forward,  at  once;  or,  if  a 
still  greater  effect  is  needed,  this  muscle  should  be  ad- 
vanced straight-forward.  In  either  case  the  tension  of 
the  muscle  would  be  increased,  but  its  plane  would  not 
be  changed.  At  the  time  the  partial  tenotomy  is  done, 
if  there  is  doubt  as  to  whether  enough  has  been  accom- 
plished, nothing  more  should  be  done  at  that  time. 
Later,  if  found  necessary,  the  externus  should  be  short- 
ened. 

In  all  uncomplicated  cases  of  esotropia  that  cannot  be 
cured  or  greatly  helped  by  non-operative  means,  three 
operations — advancement  of  the  externus,  a  partial  te- 
notomy of  the  internus  of  the  deviating  eye,  and  (a  little 
later)  a  partial  tenotomy  of  the  internus  of  the  good 
eye — should  be  done;  and  a  fourth  operation — shorten- 
ing or  advancement  of  the  externus  of  the  good  eye- 
may  be  demanded.  If  these  operations  are  carefully 
done,  the  result  should  be  a  restoration  of  the  power  of 
binocular  single  vision. 


ESOTROPIA.  555 

If  esotropia  is  complicated  by  a  hypertropia  of  one  eye 
and  catatropia  of  the  other  and  there  is  no  cyclotropia, 
the  operations  for  the  cure  of  the  esotropia  should  be 
done  as  if  there  were  no  complication — that  is,  by  alter- 
ing- the  tension  of  the  lateral  recti  in  such  a  way  as  not 
to  make  the  slightest  change  in  their  planes  of  rotation. 
Later,  or  even  simultaneously,  the  vertical  error  should 
be  treated  as  will  be  set  forth  in  connection  with  the 
study  of  the  vertical  deviations. 

If  esotropia  is  complicated  by  cyclotropia,  the  opera- 
tions done  for  altering  tension  should  be  so  done  as  to 
change  the  planes  of  rotation  also.  In  esotropia  with 
plus  cyclotropia,  but  no  hypertropia,  the  partial  tenot- 
omies  of  both  interni  should  be  marginal,  including  all 
of  the  lower  and  central  fibers,  and  equal  in  extent, 
leaving  uncut  the  upper  fibers,  thus  altering  tension  and 
elevating  the  planes  of  rotation;  and  the  shortenings  or 
advancements,  equal  in  extent,  of  both  externi  should  be 
done  so  as  to  give  them  a  lower  attachment,  unless  it  is 
shown  by  tests  that  the  marginal  tenotomies  of  the  in- 
terni, which  should  always  be  done  first,  have  fully  cor- 
rected the  plus  cyclotropia.  If  the  plus  cyclotropia  has 
been  cured  by  the  marginal  tenotomies  of  the  interni,  the 
remaining  part  of  the  esotropia  should  be  treated  by 
straight-forward  advancements  or  shortenings  of  the 
externi. 


556  ESOTROPIA. 

If  esotropia  is  complicated  by  plus  cyclotropia  of  both 
eyes  and  right  hypertropia  and  left  catatropia,  the  fol- 
lowing plan  of  operating  should  be  adopted:  First,  an 
advancement  of  the  externus  of  the  right  eye  so  as  to 
lower  its  plane  of  rotation.  This  would  counteract,  in 
part,  the  esotropia,  the  cyclotropia,  and  the  right  hyper- 
tropia; for  the  muscle,  by  means  of  its  new  attachment, 
would  pull  the  eye  toward  the  temple,  draw  it  down, 
and  tort  it  in.  The  second  operation  should  be  done  on 
the  internus  of  the  left  eye,  and  it  should  be  a  partial 
teuotomy,  including  all  the  lower  and  central  fibers  and 
leaving  uncut  only  the  fibers  at  its  upper  margin.  By  a 
reduction  of  the  tension  of  this  internus,  the  externus 
will  draw  this  eye  toward  the  temple,  while  the  upper 
uncut  fibers  of  the  internus  will  pull  the  eye  up  and  tort 
it  in.  Thus  the  esotropia  will  be  further  corrected,  and 
the  plus  cyclotropia  and  the  catatropia  will  be  wholly, 
or  in  greater  part,  corrected.  Any  remaining  esotropia 
must  be  counteracted  by  a  central  partial  tenotomy  of 
the  right  internus,  and,  if  necessary,  a  straight-forward 
advancement  of  the  left  externus,  for  the  reason  that  if 
by  the  first  two  operations  the  vertical  heterotropia  and 
the  plus  cyclotropia  have  been  cured,  the  remaining  eso- 
tropia would  be  uncomplicated  and  should  be  so  treated, 
and  for  the  further  reason  that  should  there  still  remain 
some  of  both  complications  after  the  first  two  opera- 


ESOTROPIA.  557 

tions,  elevation  of  the  plane  of  the  right  internus  would 
increase  the  hypertropia  while  lessening-  the  plus  cyclo- 
tropia,  and  lowering  the  plane  of  the  left  externus 
would  increase  the  catatropia,  while  lessening  the  plus 
cyclotropia.  In  such  a  case,  therefore,  the  planes  of  ro- 
tation of  the  right  internus  and  the  left  externus  should 
not  be  changed,  although  it  may  be  necessary  to  alter 
their  tension.  Any  vertical  heterotropia  and  plus  cyclo- 
tropia remaining  after  the  first  two  operations,  should  be 
corrected  by  a  partial  tenotomy  of  the  superior  rectus  of 
the  right  eye,  including  all  of  its  nasal  fibers  and  as 
many  of  its  central  fibers  as  might  be  necessary.  Should 
there  still  remain  some  of  the  left  catatropia  and  plus 
cyclotropia,  a  partial  tenotomy  of  the  left  inferior  rectus 
should  be  done,  including  all  the  temporal  fibers  and  as 
few  as  possible  of  the  central  fibers.  The  six  operations 
performed  in  the  order  named,  and  done  with  proper 
care,  should  cure  the  worst  case  of  this  kind.  The  only 
remaining  operations  that  should  be  done  in  such  a  case 
are:  advancement  of  the  nasal  margin  of  the  right  in- 
ferior rectus  and  advancement  of  the  temporal  margin 
of  the  left  superior  rectus,  the  indication  for  which 
would  be  some  remaining  plus  cyclotropia  with  right 
hypertropia  and  left  catatropia.  The  first  four  opera- 
tions usually  accomplish  everything  that  could  be  de- 
sired. To  ignore  the  vertical  heterotropia  when  com- 


558  ESOTROPIA. 

plicated  by  plus  cyclotropia,  or  to  ignore  the  plus  cyclo- 
tropia  when  it  is  the  only  complication,  in  operating"  for 
esotropia,  is  to  fail  to  cure  the  patient. 

By  far  the  most  troublesome  cases  of  esotropia — the 
incurable  cases,  under  the  old  methods  of  operating  — 
are  those  complicated  by  plus  cyclotropia  and  double 
h}7pertropia.  The  primary  deviation  is  in  and  up,  and 
the  eye  is  torted  out;  likewise,  the  secondary  deviation 
is  in  and  up,  and  the  eye  is  torted  out.  In  these  cases 
the  double  hypertropia  and  the  plus  cyclotropia  are  both 
caused  by  over-action  of  the  inferior  obliques,  while  the 
whole  of  the  esotropia  is  caused  by  over-action  of  the 
two  interni,  a  large  part  of  this  over-action  of  the  in- 
terni  being  in  the  nature  of  spasm.  In  some  of  these 
cases  a  division  of  the  two  inferior  obliques  will  cure 
the  double  hypertropia,  the  plus  cyclotropia,  and  the 
esotropia;  and  this  was  doubtless  the  operation  done 
by  the  quack,  Taylor,  referred  to  in  the  first  part  of 
this  chapter.  The  author  has  done  this  operation  once, 
recently,  and  with  gratifying  results.  These  cases  al- 
ways carry  their  heads  high,  but  they  should  be  care- 
fully studied  otherwise  than  as  to  the  pose  of  the  head. 
In  the  more  aggravated  cases  of  this  character,  cutting 
across  the  inferior  obliques  by  means  of  a  Graefe  knife, 
being  careful  not  to  injure  the  infraorbital  vessels  and 
nerves,  is  probably  the  best  method  of  procedure.  If 


ESOTROPIA.  559 

the  inferior  obliques  are  not  to  be  cut  in  these  cases,  the 
first  two  operations  should  be  done  on  the  superior  recti, 
at  the  same  time,  and  should  consist  of  a  division  of  all 
the  nasal  and  central  fibers  of  each,  leaving-  uncut  only 
the  temporal  margins.  These  operations  would  lower 
the  two  eyes,  and  the  uncut  temporal  fibers  would  tort 
both  eyes  in.  In  some  of  these  cases  these  two  opera- 
tions go  far  toward  curing,  not  only  the  double  hyper- 
tropia and  the  plus  cyclotropia,  but  also  the  esotropia. 
The  next  two  operations,  to  be  done  at  the  same  time  or 
with  a  short  interval  between,  are  advancements  of  both 
externi.  These  operations  should  be  done  to  increase 
the  tension  of  these  muscles,  so  as  to  counteract  the  eso- 
tropia, and  lower  their  new  attachments,  so  as  to  still 
further  correct  the  double  hypertropia  and  the  plus  cy- 
clotropia. Usually  nothing  else  will  have  to  be  done. 
Should  there  remain,  after  these  four  operations,  some 
of  the  double  hypertropia  and  plus  cyclotropia,  the  nasal 
margins  of  both  inferior  recti  should  be  advanced.  Any 
remaining  esotropia  should  be  corrected  by  a  central  par- 
tial tenotomy  of  one  or  both  interni,  in  such  a  way  as  not 
to  change  the  plane  of  rotation;  for  to  elevate  the  plane 
would  be  to  increase  any  uncorrected  nypertropia,  while 
lessening  any  uncorrected  plus  cyclotropia . 

Since  minus  cyclotropia,  as  a  complication  of  esotro- 
pia, is  so  very  rare,  it  is  only  necessary  to  say  that,  in 


560  EXOTROPIA. 

operating1  on  the  interni,  their  planes  should  be  de- 
pressed; and  in  operating1  on  the  externi,  their  planes 
should  be  elevated,  this  being-  the  very  reverse  of  what 
should  be  done  when  there  is  plus  cyclotropia. 

If  a  patient  should  be  unwilling  to  undergo  all  the 
operations  that  might  be  necessary  for  correcting  his 
comitant  esotropia,  he  may  have  the  reflex  nervous  symp- 
toms relieved  by  submitting  to  one  operation — namely, 
a  partial  tenotomy  of  the  internus  of  the  fixing  eye. 
This  would  relieve  the  nervous  tension  of  the  externus 
of  this  eye,  without  risk  of  interfering  with  the  comi- 
tant movements  of  the  two  eyes,  but  it  would  not  correct 
the  esotropia. 

EXOTROPIA. 

This  condition,  the  opposite  of  esotropia,  shows  itself 
in  such  a  deviation  of  one  eye  that  its  visual  axis,  instead 
of  intersecting  the  visual  axis  of  the  fixing  eye  at  the 
point  of  view,  deviates  from  it.  It  is  generally  taught 
that  myopia  is  one  of  the  factors  in  its  production.  As 
taught  in  a  previous  chapter,  pseudo-exophoria  manifests 
itself  only  in  the  near;  so  it  would  appear  that  myopia, 
on  which  pseudo-exophoria  depends,  could  have  nothing 
to  do  directly  in  the  causation  of  an  exotropia  that  shows 
itself  when  the  point  of  view  is  in  the  distance.  My- 
opia does  cause  exotropia  to  be  greater  in  the  near  than 
in  the  far.  The  true  cause  of  exotropia  is  intrinsic  ex- 


EXOTROPIA.  561 

ophoria.  In  a  myope  the  exotropia  first  shows  itself  in 
the  near,  when  the  pseudo-exophoria  is  grafted  on  the 
intrinsic  exophoria,  the  two  tog-ether  producing-  the  exo- 
tropia. Beginning-  in  the  near,  the  exotropia  will  show 
itself  later  in  the  distance  also,  for  the  reason  that  the 
mind,  learning-  to  disreg-ard,  in  near  work,  the  images  on 
the  retina  of  the  deviating-  eye,  becomes  able  to  suppress 
the  images  of  distant  objects,  and  this  suppression  leads 
to  the  conversion  of  the  exophoria  into  exotropia.  In 
this  way  myopia  does  contribute  to  the  production  of 
exotropia.  An  early  cure  of  the  pseudo-exophoria,  by  a 
full  correction  of  the  myopia,  prevents  an  exotropia  in 
the  near  that  does  not  exist  in  distant  vision,  and  the 
intrinsic  exophoria  may  remain  unchanged  throug-h  life. 
If  myopia  were  as  common  as  hyperopia,  exotropia  would 
be  found  as  often  as  esotropia;  for  intrinsic  exophoria 
exists  in  fully  as  many  cases  as  does  intrinsic  esophoria. 
Exotropia  may  depend  only  on  the  excessive  strength 
of  the  externi  as  contrasted  with  the  interni.  This  dif- 
ference in  relative  streng-th  may  be  due  to  hyper-devel- 
opment of  the  externi  or  subnormal  development  of  the 
interni,  or  to  the  fact  that  the  externi  have  a  more 
advantag-eous  attachment  to  the  globe  than  have  the  in- 
terni. Associated  with  either  the  one  or  the  other  of 
these  conditions,  there  may  be  a  deficiency  in  the  third 
conjug-ate  innervation  center.  While  the  chief  cause— 


562  EXOTROPIA. 

the  sole  cause  in  most  cases — may  be  in  the  excessive 
strength  of  the  externi,  the  obliques  may  also  enter 
into  the  causation,  and  that,  too,  without  there  being 
any  imbalance  of  the  obliques.  If  the  obliques  are  hy- 
per-developed, or  if  they  are  attached  too  far  behind  the 
equator,  or  if  they  are  too  short'  and  tense,  they  will 
help  the  too  strong  externus  to  turn  the  eye  out.  If,  in 
any  case  of  exophoria,  disease  or  injury  should  greatly 
reduce  the  vision  of  one  eye,  it  will  become  exotropic  in 
time.  In  anisometropia,  if  there  is  exophoria,  the  worse 
eye  eventually  will  turn  outward,  in  many  cases.  A 
congenitally  low  state  of  vision  in  one  eye,  when  there  is 
exophoria,  will  favor  its  transformation  into  exotropia. 
It  is  doubtful  if  "antipathy  to  binocular  single  vision" 
is  as  often  a  cause  of  exotropia  as  it  is  of  esotropia. 

The  chief  cause  of  many  cases  of  exotropia  has  been 
traumatism;  and,  unfortunately  for  science,  it  has  been 
operative  traumatism.  "Straightening  crossed  eyes  in 
a  minute  "  has  most  often  resulted  in  a  perpetual  out- 
turning.  But  in  the  past,  complete  tenotomies  of  the 
interni  for  esotropia,  performed  by  both  general  and 
ophthalmic  surgeons,  because  they  had  been  taught  to 
do  so  by  such  masters  as  Dieffenbach  and  Graefe,  re- 
sulted often,  in  a  year  or  two,  in  an  exotropia  that  was 
not  comitant.  Such  a  disaster  has  happened  to  every 
surgeon  who  has  made  many  complete  tenotomies  of  the 


EXOTROPIA.  563 

interni,  even  when  he  was  most  careful  not  to  cut  the 
check  ligaments.  It  is  true  that  exotropia  has  not  fol- 
lowed all  the  complete  tenotomies  of  the  interni  that 
have  been  made,  else  surgeons  would  have  ceased,  long- 
ago,  to  attempt  thus  to  relieve  patients  of  one  deformity 
simply  to  bring1  on  them  another,  even  more  objectiona- 
ble. Thanks  to  the  long-  and  strong-  insistence  of  Lan- 
dolt,  that  advancements  should  supplant  tenotomies,  the 
days  of  complete  tenotomies  of  the  interni  are  numbered. 
Even  Panas'  operation  cannot  long-  delay  the  total  aban- 
donment of  complete  tenotomies  for  the  relief  of  esotro- 
pia  or  any  other  form  of  heterotropia.  Then  no  case  of 
exotropia  will  result  from  surgery. 

While  comitant  exotropia  may  show  itself  in  only  one 
eye,  it  is,  nevertheless,  a  binocular  trouble,  which  should 
not  be  forgotten  at  the  time  treatment  is  instituted. 
Exotropia  always  begins  later  in  life  than  esotropia. 
Exotropia  may  be  alternating  early  in  the  history  of  a 
case,  but  it  soon  becomes  the  fixed  habit  of  one  eye,  usu- 
ally the  one  that  has  conditions  most  favorable  to  mental 
suppression  of  images — a  habit  that  is  acquired  by  exo- 
tropes  as  well  as  by  esotropes. 

The  complications  of  exotropia  are  errors  of  refraction 
(myopic  refraction  helps  to  cause  exotropia) ;  double  hy- 
pertropia  and  double  catatropia;  hypertropia  of  one  eye 
and  catatropia  of  the  other;  and  symmetrical  or  non- 


564  EXOTROPIA. 

symmetrical  cyclotropia.  Treatment  of  the  complica- 
tions must  constitute  a  part  of  the  treatment  of  the 
chief  condition,  and,  for  this  reason,  they  should  not  be 
ignored  in  any  case. 

The  amount  of  exotropia  can  be  determined  readily, 
by  any  one  of  the  methods  resorted  to  for  measuring 
esotropia,  by  a  reversal  of  every  step. 

SYMPTOMS. — The  symptoms  of  exotropia  are  objec- 
tive and  subjective.  The  only  objective  symptom  is 
the  disfigurement,  which  is  greater  or  less,  in  pro- 
portion to  the  extent  of  the  outward  turning-.  Am- 
blyopia,  in  many  cases,  is  the  only  subjective  symp- 
tom; and  this — in  some  cases,  at  least  —  has  been 
acquired  by  the  power  of  mental  suppression.  Exo- 
phoria  is  attended,  practically  always,  by  reflex  symp- 
toms, as  already  shown;  but  reflex  symptoms  are  rare 
in  exotropia.  The  reflex  symptoms  found  in  a  case 
of  exotropia  are  due  either  to  the  nervous  tension  of 
the  internus  of  the  fixing-  eye  or  to  some  one  or  more  of 
the  complications.  Exotropes  who  have  been  made  so 
by  complete  tenotomies  of  the  interni  are  more  liable  to 
show  reflexes,  and  for  the  reason  that  the  out-turned 
eye  cannot  move  comitantly  with  its  fellow.  It  is  the 
generation  of  the  excessive  impulse — the  unbalanced  im- 
pulse—  to  force  comitant  movements  that  cannot  be 
forced,  which  brings  about  the  reflex  disturbances.  To 


EXOTROPIA.  565 

illustrate:  Suppose  that  the  right  internus  has  been  cut, 
resulting*  in  a  non-comitant  exotropia.  When  the  eyes 
are  made  to  move  to  the  right,  there  must  be  abnormal  ac- 
tion of  the  fourth  conjugate  center;  for  the  left  internus, 
being-  opposed  by  an  uncrippled  externus,  will  require  a 
greater  impulse  for  a  certain  movement  of  its  eye  to  the 
right  than  will  the  externus  of  the  right  eye,  which  is 
opposed  by  a  crippled  internus.  It  is  the  fourth  conju- 
gate brain-center  that  effects  this  rotation,  and  it  cannot 
act  normally  under  such  a  condition.  In  such  a  case, 
when  the  eyes  are  rotated  toward  the  left,  it  must  be 
through  the  fifth  conjugate  brain-center,  which  will  at- 
tempt the  impossible  task  of  making  the  crippled  right 
internus  move  its  eye  comitantly  with  the  fellow  eye 
whose  externus  is  not  crippled.  The  impossibility  of 
accomplishing  the  task  does  not  prevent  the  brain-center 
from  undertaking  it.  Disturbance  of  one  brain-center 
can  excite  sympathetic  disturbance  in  any  other  brain- 
center. 

One  of  the  worst  neurotic  conditions  that  the  author 
has  ever  seen  was  in  a  patient  who  had  a  non-comitant 
exotropia  which  had  resulted  from  a  complete  tenotomy 
of  his  right  internus,  performed  many  years  before.  His 
case  was  diagnosed  as  an  organic  brain  disease,  and  he 
was  treated  accordingly  for  two  or  more  years  without 
improvement.  That  his  troubles  were  all  reflex,  and 


566  EXOTROPIA. 

that  the  cause  was  his  non-comitant  exotropia,  cannot  be 
doubted,  for  he  recovered  quickly  after  the  enucleation 
of  his  exotropic  eye,  which  operation  was  done  at  his 
own  earnest  solicitation ;  he  even  demanded  that  it 
should  be  done,  believing-,  as  he  did,  that  this  was  his 
only  chance.  His  belief  that  his  troubles  were  referable 
to  the  condition  of  his  right  eye  was  based  on  temporary 
relief  which  he  experienced  two  years  previously  from 
an  advancement  operation  on  the  right  internus,  per- 
formed by  the  author,  with  an  incomplete  result  as  to 
position  and  movement.  Later,  an  operation  was  done 
on  the  right  superior  rectus  for  a  complicating  hypertro- 
pia,  with  renewed  relief  of  some  of  the  symptoms  that 
had  again  become  prominent.  Later,  the  author  ex- 
pected, and  promised,  to  bring  the  right  internus,  atro- 
phied as  it  was,  still  farther  forward.  The  symptoms 
became  aggravated  again,  and  the  patient  returned  for 
the  promised  operation.  A  colleague,  Dr.  J.  A.  Wither- 
spoon,  of  Nashville,  skilled  in  neurology,  was  called  in 
consultation.  The  Doctor  pronounced  the  case  one  of  or- 
ganic brain  disease,  the  author  agreeing  with  him.  No 
other  operation  was  attempted.  The  patient  was  placed 
entirely  in  the  hands  of  the  consultant,  who  treated 
him  without  results.  In  a  few  months  the  patient 
was  induced  to  go  to  Battle  Creek  Sanitarium,  where 
he  remained  for  nearly  two  years  without  any  marked 


EXOTROPIA.  567 

change  in  his  condition,  either  for  better  or  worse.  It 
was  while  there  that  he  insisted  on  the  operation  of  enu- 
cleation,  which  was  done. 

The  above  case  is  thus  fully  reported  to  emphasize  the 
point  that  a  comitant  heterotropia  of  one  kind  should 
never  be  converted  into  a  non-comitant  heterotropia  of 
another  kind,  to  avoid  which  one  should  be  careful  never 
to  do  a  complete  tenotomy  of  any  rectus  muscle  for  any 
condition. 

In  this  connection  it  may  be  said  that,  in  all  probabil- 
ity, Dr.  John  Dunn,  of  Richmond,  Va.,  was  the  first 
operator  to  enucleate  one  eye  in  which  there  was  good 
vision,  to  relieve  the  patient  of  severe  nervous  symptoms 
caused  by  what  was  considered  a  hopeless  muscle  im- 
balance. The  operation  cured  the  patient.  This  case 
has  not  been  reported. 

Another  case  may  be  referred  to  also,  somewhat  like 
the  two  preceding  cases  as  to  results,  though  the  method 
of  obtaining  them  was  unlike  that  resorted  to  in  the 
other  cases.  This  case  was  that  of  a  young  lawyer  who 
suffered  so  much  with  his  head  and  eyes  that  he  contem- 
plated giving  up  his  profession,  having  failed  to  get  re- 
lief from  cylinders  which  he  needed,  from  prisms  which 
he  did  not  need,  and  from  ceiling-to-floor  and  wall-to- 
wall  exercise,  which,  for  some  reason,  he  was  unable  to 
do  for  even  one  minute  without  suffering.  There  was 


568  EXOTROPIA. 

no  heterophoria,  but  the  muscles  were  "balanced  in 
weakness,"  as  shown  by  the  fact  that  his  abduction  was 
two  degrees;  his  adduction,  less  than  ten  degrees;  his 
sub-duction  and  superduction,  one  degree.  The  vision 
of  his  rig-lit  eye  was  ||;  that  of  the  left  eye,  |£.  Every 
means  that  had  been  suggested  by  any  one  of  the  several 
ophthalmic  surgeons  whom  he  had  consulted  had  been 
tried,  and  failure  had  resulted  from  all.  At  last  the 
author  advised  him  to  have  his  left  eye  rendered  useless. 
He  consented,  and  the  left  lens,  already  slightly  opaque, 
accounting  for  the  reduced  vision,  was  carefully  needled, 
so  as  to  render  it  densely  opaque  without  effecting  its 
solution.  The  comfort  which  he  had  been  seeking  came 
as  a  result  of  this  operation.  It  has  been  one  year  and 
a  half  since  the  operation  was  done,  and  there  has  been 
no  return  of  his  symptoms.  Nothing  else  than  making 
the  one  eye  blind,  or  removing  it,  could  have  cured  him, 
except  the  shortening  of  all  the  recti  muscles,  and  it 
is  doubtful  if  that  would  have  done  it.  These  shorten- 
ings the  author  would  have  advised  if  the  lens  in  his  left 
eye  had  been  perfectly  transparent  and  vision  had  been 
good. 

These  three  cases  are  reported  here,  though  not  prop* 
erly  connected,  because  of  the  results  that  followed  so 
radical  operations,  after  all  other  means  had  failed. 
These  three  patients,  operated  on  by  three  different  men, 


EXOTROPIA.  569 

would  agree  that  it  is  better  to  go  through  life  with  only 
one  eye  than  to  have  two  eyes  that  would  be  a  constant 
source  of  suffering.  If  relief  can  be  obtained  short  of 
sacrificing  one  eye,  so  repulsive  an  operation  as  enuclea- 
tion  should  be  avoided. 

TREATMENT  OF  EXOTROPIA. 

The  correction  of  myopia  early  in  the  history  of  an 
exotropia — that  is,  when  there  is  exotropia  in  the  near, 
but  none  in  the  far — by  removing  the  pseudo-exophoric 
factor,  may  correct  the  exotropia,  reconverting  the  exo- 
tropia into  an  intrinsic  exophoria.  But  the  correction  of 
the  exotropia  by  means  of  the  concave  lenses  is  not  a 
cure,  in  the  proper  sense;  the  intrinsic  exophoric  factor 
must  also  be  removed,  and  this  can  be  done,  in  such  a 
case,  only  by  partial  tenotomies  of  the  externi  or  by 
shortenings  or  advancements  of  the  interni. 

In  simple  uncomplicated  exotropia,  at  least  three  op- 
erations should  be  performed.  Two  operations  on  the 
deviating  eye  should  be  done  first.  One  of  these  should 
be  a  partial  tenotomy  of  the  externus,  so  done  as  to  les- 
sen its  tension  without  changing  its  plane  of  rotation — a 
central  partial  tenotomy;  and  at  the  same  time  the  oppos- 
ing internus  should  be  either  shortened  or  advanced,  and 
in  such  away  as  to  increase  its  tension  without  changing 
its  plane  —  a  straight-forward  shortening  or  a  straight- 


570  EXOTROPIA. 

forward  advancement.  At  any  time  after  one  week,  a 
partial  tenotomy  of  the  externus  of  the  fellow  eye  should 
be  made,  and  in  such  a  way  as  to  lessen  its  tension  without 
changing  its  plane — a  central  partial  tenotomy.  If  these 
three  operations  do  not  properly  relate  the  eyes,  a  fourth 
operation  should  be  done,  at  any  time  after  two  to  four 
weeks.  This  operation  should  be  a  shortening  or  an  ad- 
vancement of  the  internus  of  the  good  eye,  and  it  should 
be  so  done  as  to  increase  its  tension  without  changing  its 
plane — a  straight-forward  shortening  or  a  straight-for- 
ward advancement.  A  very  slight  simple  exotropia  may 
be  cured  by  central  partial  tenotomies  of  the  two  externi, 
performed  at  the  same  time;  but  most  cases  will  require 
three,  if  not  four,  operations.  If  these  operations  have 
been  performed  in  the  order  and  after  the  manner  set 
forth  above,  the  operator  need  have  no  fear  that  his  case, 
which  wras  comitant  exotropia  before  the  operations,  will 
become  non-comitant  esotropia  later;  nor  need  he  have 
any  fear  that  a  torsioning  of  the  eyes  will  result.  In 
exotropia  of  medium  or  high  degree,  the  operation  on  the 
weak  interni  must  be  an  advancement,  for  a  shortening 
cannot  produce  enough  effect. 

An  exotropia  complicated  with  a  double  hypertropia,  a 
double  catatropia,  or  a  hypertropia  of  one  eye  and  a  cata- 
tropia  of  the  other,  would  require  for  its  relief  the  same 
kind  of  operations  as  if  there  were  no  complication  — 


EXOTROPIA.  571 

that  is,  the  partial  tenotomies  of  the  extern!  should  be 
central,  so  as  to  lessen  tension  without  a  change  of 
plane;  and  the  shortenings  or  advancements  of  the  in- 
terni  should  be  straight  forward,  so  as  to  increase  ten- 
sion without  a  change  of  the  plane  of  rotation.  In  the 
course  of  the  treatment,  the  vertical  heterotropia  should 
be  relieved  in  the  manner  to  be  shown  in  the  study  of  hy- 
pertropia  and  catatropia,  uncomplicated  by  cyclotropia. 

If  exotropia  is  complicated  by  plus  cyclotropia  only, 
the  order  of  operating,  as  well  as  the  method,  should  be 
changed.  The  two  operations  to  be  done  first,  and  in 
immediate  succession,  should  be  performed  on  both  ex- 
terni,  and  should  consist  of  a  marginal  tenotomy  of  each, 
the  cut  including  the  upper  and  central  fibers,  the  lower 
fibers  to  remain  intact.  These  operations  would  lessen 
the  tension  of  both  externi,  and  would  lower  their  planes 
of  rotation,  so  that,  in  their  new  relationship,  they  would 
tort  the  eyes  in.  This  change  of  plane  would  also  cause 
a  double  cataphoria.  The  operative  effect  on  the  two 
muscles  should  be  as  nearly  equal  as  possible,  so  as  to  tort 
both  eyes  in  alike  and  depress  them  equally.  After  these 
two  operations,  if  some  of  the  plus  cyclotropia,  as  well  as 
some  of  the  exotropia,  should  remain,  both  interni  should 
be  shortened  or  advanced  equally,  and  in  such  a  manner 
as  to  elevate  their  planes  of  rotation.  The  amount  of 
increase  of  tension  and  the  extent  of  the  elevation  of  the 


572  EXOTROPIA. 

planes  would  have  to  be  gauged  according  to  the  best 
judgment  of  the  operator.  The  end  in  view  should  be 
perfect  control  of  the  visual  axes  and  the  paralleling  of 
the  vertical  axes  with  the  median  plane  of  the  head.  If 
the  two  marginal  tenotomies  should  correct  the  whole  of 
the  plus  cyclotropia,  the  remaining  exotropia  should  be 
corrected  by  straight  -  forward  shortening  or  advance- 
ment— first,  of  the  internus  of  the  deviating  eye;  and 
later,  if  necessary,  of  the  internus  of  the  good  eye. 

If  exotropia  is  complicated  with  plus  cyclotropia,  right 
hypertropia,  and  left  catatropia,  the  operations  on  the  lat- 
eral recti  should  be  done  so  as  to  alter  their  tension  and 
change  their  planes  of  rotation,  the  latter  only  up  to  the 
point  of  a  full  correction  of  the  plus  cyclotropia.  The 
operations  should  be  done  in  the  following  order,  with  two 
or  more  weeks  intervening:  The  first  operation  should  be 
a  marginal  partial  tenotomy  of  the  externus  of  the  hyper- 
tropic  eye,  including  the  upper  and  central  fibers.  The 
effect  of  this  would  be  (1)  to  lessen  its  tension,  so  that  the 
internus  might  draw  the  eye  in;  (2)  lowering  the  plane  so 
as  to  tort  the  eye  in,  to  counteract  the  plus  cyclotropia, 
and  at  the  same  time  (3)  turn  the  eye  down  for  counteract- 
ing the  right  hypertropia.  The  second  operation  should 
be  a  shortening  or  an  advancement  of  the  left  internus, 
so  as  to  increase  its  tension  and  elevate  its  plane;  and, 
that  this  may  be  done,  not  over  half  of  the  correction  of 


EXOTROPIA.  573 

the  main  error  and  its  complications  should  be  attempted 
in  the  first  operation.  The  effect  of  the  second  opera- 
tion would  be  (1)  to  increase  its  tension  so  as  to  enable 
it  to  draw  the  eye  in;  (2)  to  tort  the  eye  in,  b}^  means  of 
the  elevation  of  the  plane,  so  as  to  counteract,  if  possible, 
the  remaining  plus  cyclotropia;  and  (3)  to  elevate  the  eye, 
to  still  farther — and,  if  possible,  entirely — relieve  the  re- 
maining part  of  the  left  catatropia.  If,  for  the  farther 
relief  of  the  exotropia  (whether  or  not  there  may  have 
remained  from  the  first  two  operations  some  of  the  plus 
cyclotropia),  it  becomes  necessary  to  operate  on  the  in- 
ternus  of  the  right  eye  and  the  externus  of  the  left  eye, 
each  of  these  operations  would  have  to  be  done  so  as  to 
alter  tension  without  changing  the  plane  of  rotation— 
that  is,  the  shortening  or  the  advancement  of  the  right 
internus  would  have  to  be  straight-forward,  and  the  par- 
tial tenotomy  of  the  left  externus  would  have  to  be  cen- 
tral. The  reason  for  this  is  clear:  To  elevate  the  plane 
of  the  right  internus  would  help  to  correct  any  remain- 
ing plus  cyclotropia,  in  itself  desirable,  but  this  would 
also  elevate  the  eye — a  thing  not  to  be  desired;  to  depress 
the  plane  of  the  left  externus  \vould  correct  any  remain- 
ing plus  cyclotropia,  in  itself  desirable,  but  it  would  de- 
press still  farther  the  eye  that  is  already  too  low. 

It  is  so  very  rare  that  a  minus  cyclotropia  is  found  com- 
plicating an  exotropia,  it  is  only  necessary  to  say  that, 


574  EXOTROPIA. 

when  it  does  exist,  both  the  order  of  operating  and  the 
method  of  doing-  each  operation,  looking  toward  a  change 
of  the  muscle  plane,  should  be  the  reverse  of  what  has 
been  advised  when  plus  cyclotropia  is  the  complication. 

When  exotropia  is  complicated  by  a  double  hypertro- 
pia  and  plus  cyclotropia,  it  is  probable  that  both  compli- 
cations are  caused  by  the  inferior  obliques,  and  that  these 
muscles  have  also  entered  largely  into  the  causation  of 
the  exotropia.  The  operation  most  plainly  indicated  is  a 
division  of  the  inferior  oblique  of  both  the  deviating  eye 
and  the  fixing  eye.  If  it  were  possible,  in  doing  these 
operations,  to  leave  some  of  its  fibers  uncut,  it  would  be 
better.  But  a  hook  and  scissors  cannot  be  used,  and  the 
division  must  be  effected  by  passing  a  Graefe  knife  above 
and  beyond  the  muscle  and  between  its  origin  and  the 
course  of  the  infraorbital  vessels  and  nerves,  with  the 
cutting  edge  of  the  knife  looking  toward  the  orbital 
floor,  then,  bringing  the  knife  down,  dividing  every  struc- 
ture between  it  and  the  orbital  floor.  Again,  the  author 
will  say  that  he  has  done  this  operation  on  only  one  case, 
and  the  result  was  highly  satisfactory.  He  would  not 
hesitate  to  do  it  again  in  a  case  so  well  marked. 

If  the  case  is  not  sufficiently  exaggerated  to  justify  a 
complete  division  of  the  inferior  obliques,  or  if  these  have 
been  divided,  but  some  of  the  main  error  with  both  of  its 
complications  remains,  a  marginal  tenotomy  of  both  ex- 


SXOTROPIA. 

terni  should  be  done,  including  the  upper  and  central 
fibers.  This  would  lessen  their  tension,  so  as  to  allow 
the  eyes  to  be  drawn  toward  each  other  by  the  intern i,  and 
the  lower  uncut  fibers  \vould  depress  the  eyes  and  would 
tort  them  in.  To  make  shortenings  or  advancements  of 
the  interni  with  the  view  not  only  of  increasing  their 
tension,  but  also  of  changing  their  planes  of  rotation 
would  be  wrong;  for  elevating  these  planes  would  raise 
the  eyes  still  higher,  while  counteracting  the  plus  cyclo- 
tropia — hurtful  in  one  result,  while  helpful  in  the  other. 
It  is  clear,  therefore,  that,  in  such  a  case,  if  the  tension 
of  the  interni  must  be  increased  to  still  further  correct 
the  exotropia,  the  shortenings  or  advancements  should 
be  straight-forward. 

At  the  meeting  of  the  American  Medical  Association  in 
Atlantic  City,  N.  J.,  in  1900,  L.  Webster  Fox,  of  Philadel- 
phia, read  before  the  section  of  ophthalmology  a  paper, 
entitled  '  'A  Simple  Operation  for  Divergent  Strabismus. ' ' 
He  stated  in  this  paper  that  he  had  put  to  a  test  the  vari- 
ous accepted  methods  for  correcting  this  error,  and  that 
he  had  noted  the  difficulties  and  many  failures  in  his  own 
practice,  such  as  had  been  experienced  by  others.  This 
led  him  to  devise  the  method  which  he  wished  to  de- 
scribe, and  for  the  reason  that,  through  a  period  of 
eight  years,  it  had  given  him  satisfaction.  At  the  au- 
thor's request,  Dr.  Fox  has  furnished  the  cuts  to  illus- 


576  EXOTROPIA. 

trate  the  text.     The  method  of  procedure  will  be  given 
in  Fox's  own  words: 

"The  operation  is  divided  into  three  parts,  and  is  per- 
formed under  cocaine:  (1)  tenotomy  of  both  external  recti 
muscles  and  stretching*  of  conjunctiva  and  Tenon's  cap- 
sule; (2)  making-  the  elliptical  opening-  either  on  one  eye 
or  both;  (3)  suturing  this  opening-. 

"The  details  of  operation  are  carried  out  as  follows: 
"1.  Tenotomy  of  both  external  recti  muscles,  making 
an  opening-  through  the  conjunctiva,  over  the  insertion  of 
the  tendons.  I  then  stretch  Tenon's  capsule  until  the 
cornea  is  well  into  the  inner  canthus;  this  is  done  on 
both  eyes.  Panas'  method  is  to  insert  the  hook  under  the 
muscle  and  apply  pronounced  traction,  at  the  same  time 
burying  the  cornea  in  the  outer  or  inner  canthus  [inner, 
in  exotropia].  The  operation  is  performed  under  ether 
or  chloroform,  while  in  this  method  cocaine  only  is  used. 
The  stretching  of  Tenon's  capsule  is  an  important  part 
of  the  operation.  My  method  is  as  follows:  The  stra- 
bismus hook  (which  is  a  large  one),  flat  on  its  side,  is 
inserted  in  the  opened  conjunctiva  and  Tenon's  cap- 
sule, and  with  considerable  traction  all  the  tissues  are 
stretched  inward  until  the  cornea  is  buried  in  the  in- 
ner canthus.  The  stretching  of  the  upper  tissue  has, 
as  can  be  readily  understood,  a  tendency  to  rotate  the 
eyeball  to  a  certain  degree  and  leave  the  conjunctiva 


EXOTROPIA. 


577 


and  Tenon's  capsule  intact  below;  to  equalize  the 
stretching,  the  point  of  the  hook  is  reversed,  and  the 
lower  conjunctiva  and  capsule  stretched.  In  Panas' 
method  the  hook  being-  placed  under  the  external  or 
internal  muscle  prevents  rotation  of  the  eyeball. 

"  2.  With  the  retractor  forceps  I  grasp  the  conjuctiva 
verticallv,  midway  between  the  cornea  and  caruncle  and 


Fig.  76. 

directly  over  the  internal  muscle,  and  draw  upward  the 
conjunctiva  and  as  much  of  Tenon's  capsule  as  I  can.  I 
raise  the  forceps  two  or  three  times  to  take  up  as  much 
of  the  redundant  tissue  as  my  judg-ment  dictates,  and  by 
this  means  one  apparently  is  always  successful  in  sepa- 
rating- conjunctiva  and  overlying1  tissue  from  the  muscle, 
if  it  be  still  present;  then  with  curved  scissors  I  cut 


578 


EXOTROPIA. 


with  one  long1  sweep  the  upraised  conjunctiva  and  cap- 
sule close  to  the  eyeball,  making1  an  elliptic  opening,  ex- 
posing, at  times,  the  attenuated  muscle,  and,  if  no  mus- 
cle be  present,  then  the  clear  sclerotic. 


Fig.  77. 

' '  This  opening  now  extends  in  a  vertical  direction,  be- 
ginning below  the  lower  level  of  the  cornea  to  a  point 
above  the  same,  its  width  over  the  muscle  is  about  one 
full  centimeter  at  its  greatest  diameter.  The  conjuctiva 
is  then  separated  around  this  elliptic  wound  from  its  sub- 


EXOTROPIA.  579 

conjunctival  tissues  at  all  points — even  around  the  cor- 
nea, if  possible. 

"  3.  The  elliptic  opening  is  brought  together  with  four 
sutures.  The  upper  suture  is  inserted  through  conjunc- 
tiva and  Tenon's  capsule  and  across  under  conjunctiva 
and  Tenon's  capsule  midway  between  the  insertion  of 
the  superior  rectus  muscle  and  the  margin  of  the  cornea; 


Fig.  78. 

a  similar  suture  is  passed  through  the  lower  margin  of 
the  conjunctiva  and  brought  out  midway  between  the 
insertion  of  the  inferior  muscle  and  the  margin  of  the 
cornea;  this  thread  is  then  tied,  and,  in  like  manner,  the 
upper  thread;  two  more  sutures  are  passed  through  the 
margin  of  the  lips  of  the  wound  and  united. 

' '  This  constitutes  the  details  of  the  operation.  The 
object  of  the  operator  should  be  to  produce  from  one  to 
four  millimeters  of  convergence,  which  disappears  during 


580  3XOTROPIA. 

cicatrization.  When  the  defect  is  not  more  than  two  or 
three  millimeters,  I  have  performed  an  external  tenotomy 
on  both  and  stretched  Tenon's  capsule,  with  excellent 
results,  without  taking-  out  the  elliptic  section,  especially 
in  those  cases  where  the  eyes  could  be  held  by  the  patient 
at  fixed  convergence  at  ten  inches." 

Fox's  operation  has  been  thus  described,  in  his  own 
words,  for  the  reason  that  it  is  probably  the  equal  of 
Panas'  operation,  if  not  superior  to  it,  for  exotropia. 
While  it  may  be  comparatively  safe  in  exotropia,  it  cer- 
tainly would  be  very  dangerous  in  esotropia;  but  even 
in  exotropia  there  is  danger  that  a  complete  tenotomy 
may  cripple  the  comitant  lateral  movements  of  the  eyes — 
a  danger  never  encountered  when  the  stronger  muscle  is 
partially  divided,  without  any  stretching,  and  the  weaker 
muscle  is  shortened  or  advanced. 

The  form  of  exotropia  that  most  urgently  demands 
relief  is  the  non-comitant  exotropia  which  has  resulted 
from  complete  tenotomies  for  esotropia.  In  these  cases 
the  externi,  which  were  never  possessed  of  too  much 
intrinsic  strength,  should  not  be  even  partially  cut,  but 
the  whole  effect  should  be  accomplished  by  advancement 
of  the  internus  that  had  been  allowed  to  retract  too 
far.  In  these  cases  all  the  complications  must  be  con- 
sidered, and  the  advancements  should  be  governed  ac- 
cordingly. 


HYPERTROPIA  AND  CATATROPIA.  581 

HYPERTROPIA  AND  CATATROPIA. 

These  conditions  practically  always  exist  as  compli- 
cations of  either  esotropia  or  exotropia,  and  not  infre- 
quently are  associated  with  cyclotropia.  Hypertropia 
may  be  double,  and  catatropia  may  be  double,  or  there 
may  be  a  hypertropia  of  one  eye  and  a  catatropia  of  the 
other.  If  there  is  double  hypertropia  without  cyclo- 
tropia, the  error  is  caused  by  the  conjoined  action  of  the 
superior  recti  and  the  inferior  obliques,  both  of  which 
elevate  the  eye,  while  the  in-torting  action  of  the  supe- 
rior rectus  is  counteracted  by  the  out-torting-  action  of 
the  inferior  obliques. 

If  there  is  double  hypertropia  with  minus  cyclotropia, 
the  chief  factors  in  its  production  are  the  superior  recti, 
aided,  possibly,  by  interni  whose  attachments  are  too 
high. 

If  there  is  double  hypertropia  with  plus  cyclotropia, 
the  chief  factors  are  the  inferior  obliques,  aided,  possi- 
bly, by  externi  that  are  attached  too  high. 

Double  catatropia,  if  caused  by  both  the  inferior  recti 
and  the  superior  obliques,  will  show  no  cyclotropia;  if 
caused  by  the  inferior  recti  alone,  or  with  the  aid  of  in- 
terni that  are  attached  too  low,  there  will  be  plus  cyclo- 
tropia also;  if  caused  by  the  superior  obliques  alone,  or 
with  the  aid  of  externi  whose  attachments  are  too  low, 
there  will  be  minus  cyclotropia  also. 


582  HYPERTROPIA   AND   CATATROPIA. 

When  there  is  hypertropia  of  one  eye  with  catatropia 
of  the  other,  there  will  be  no  cyclotropia  if  the  hyper- 
tropia is  caused  by  the  conjoined  action  of  the  superior 
rectus  and  the  inferior  oblique,  and  the  catatropia  is 
caused  by  the  united  action  of  the  inferior  rectus  and 
the  superior  oblique. 

If  the  hypertropia  of  the  one  eye  is  caused  by  the 
superior  rectus  alone,  or  with  the  aid  of  a  too  high  in- 
ternus,  there  will  be  minus  cyclotropia;  and  if  the  cat- 
atropia of  the  other  eye  is  caused  by  the  inferior  rectus 
alone,  or  with  the  aid  of  a  too  low  internus,  there  will 
be  plus  cyclotropia — the  two  eyes  together  would  have 
parallel  cyclotropia. 

If  the  hypertropia  of  the  one  eye  is  caused  by  the  infe- 
rior oblique  alone,  or  with  the  aid  of  an  externus  that  is 
attached  too  high,  there  will  be  also  a  plus  cyclotropia; 
and  if  the  catatropia  of  the  other  eye  is  caused  by  the 
superior  oblique  alone,  or  with  the  aid  of  an  externus 
that  is  attached  too  low,  there  will  be  also  a  minus 
cyclotropia — the  two  eyes  together  would  show  parallel 
cyclotropia. 

If  there  is  hypertropia  of  one  eye  with  catatropia  of 
the  other,  and  the  complication  is  plus  cyclotropia  of 
both  eyes,  the  cause  of  the  hypertropia  is  the  inferior 
oblique,  and  the  cause  of  the  catatropia  is  the  inferior 
rectus;  or,  if  the  complication  is  minus  cyclotropia,  the 


HYPERTROPIA  AND  CATATROPIA.        583 

cause  of  the  hypertropia  is  the  superior  rectus,  and  the 
cause  of  the  catatropia  is  the  superior  oblique. 

The  cause  of  the  vertical  heterotropias  is  in  the  mus- 
cles that  are  concerned  in  elevating-  and  depressing-  the 
eyes,  aided  in  some  cases  by  the  lateral  muscles  that  are 
attached  too  high  or  too  low.  For  the  first  year  or  two 
the  want  of  harmony  between  these  muscles  is  shown  by 
some  form  of  vertical  heterophoria,  which,  especially 
when  associated  with  some  form  of  imbalance  of  the 
laterally  acting1  muscles,  becomes  transformed  into  a 
vertical  heterotropia  at  the  same  time  that  the  lateral 
heterophoria  becomes  transformed  into  lateral  hetero- 
tropia. Hypertropia  and  catatropia  rarely  exist  alone. 
They  are  comitant  in  character,  except  when  they  are  the 
result  of  operations  or  caused  by  paralysis. 

The  disfigurement  of  the  individual  is  the  objective 
symptom;  and  the  subjective  symptoms  are  those  al- 
ready mentioned  in  connection  with  the  study  of  the 
lateral  heterotropias.  Reflex  neuroses  are  not  often 
connected  with  the  comitant  form;  but  when  they  do 
exist,  their  cause  is  abnormal  nervous  tension  of  the 
weaker  muscle  of  the  fixing  eye.  But  the  non-comi- 
tant  hypertropia  or  catatropia — nearly  always  the  lat- 
ter, for  the  reason  that  a  complete  tenotomy  of  a  su- 
perior rectus  for  a  hyperphoria  is  more  often  done 
than  a  complete  tenotomy  for  a  cataphoria— often  causes 


584  HYPERTROPIA   AND    CATATROPIA. 

severe  reflexes;  besides,  a  non-comitant  catatropia,  re- 
sulting' from  a  complete  division  of  a  superior  rectus 
for  a  hyperphoria,  in  an  adult,  is  always  attended  by 
diplopia.  At  that  age  mental  suppression  is  impossible. 
These  errors  can  be  measured  more  easily  by  the  pho- 
rometer  than  by  any  other  method,  but  the  perimeter 
and  the  tape  methods  (the  graduated  tape  to  be  held 
vertically)  can  be  resorted  to. 

TREATMENT  OF  VERTICAL  HETEROTROPIA. 

In  the  discussion  of  the  treatment  of  esotropia  and  ex- 
otropia  it  has  been  shown  that,  when  hypertropia  and 
catatropia  are  the  only  complication,  each  condition 
must  be  treated  as  thoug-h  the  other  -did  not  exist — that 
is,  every  offending-  muscle  must  have  its  tension  altered 
without  a  chang-e  of  plane.  In  the  same  manner  must 
uncomplicated  vertical  heterotropias  be  treated.  If  the 
error  is  a  double  hypertropia,  a  central  partial  tenotomy 
of  each  superior  rectus  should  be  done.  The  effect 
should  be  equally  divided  between  the  muscles,  so  as  to 
lower  the  eyes  the  same  number  of  degrees.  If  the  con- 
dition is  an  uncomplicated  double  catatropia,  a  central 
partial  tenotomy  of  both  inferior  recti  should  be  done; 
but  care  should  be  taken  not  to  do  too  much,  for  the 
reason  that  a  slight  double  catatropia  is  much  to  be  pre- 
ferred to  a  very  slight  double  hypertropia. 


HYPERTROPIA  AND  CATATROPIA.        585 

A  double  hypertropia  complicated  by  plus  cyclotropia 
is  caused  by  the  inferior  obliques.  If  these  two  errors 
are  very  high  in  degree,  and  especially  if  there  is  want 
of  converging-  power,  the  conditions  would  be  better  cor- 
rected by  cutting1  both  inferior  obliques.  These  opera- 
tions would  correct  not  only  the  double  hypertropia  and 
the  plus  cyclotropia,  but  would  also  g-ive  an  increase  of 
converging-  power.  If  these  combined  errors  are  not  so 
high  in  degree,  or  if  high  in  degree  and  there  is  little  or 
much  esotropia,  a  division  of  the  inner  and  central  fibers 
of  both  superior  recti  would  be  indicated;  for  these  op- 
erations would  correct  the  double  hypertropia  and  the 
plus  cyclotropia  and  at  the  same  time  would  lessen  con- 
vergence. 

A  double  hypertropia  complicated  by  a  minus  cyclo- 
tropia is  caused  by  the  two  superior  recti,  and  the  oper- 
ation to  be  done  is  a  marginal  tenotomy  of  both  these 
muscles,  dividing  the  temporal  and  central  fibers.  In 
such  a  case  there  is  practically  always  some  esotropia 
also,  which  will  be  slightly  increased  by  these  opera- 
tions; but  the  latter  can  be  treated  as  set  forth  under 
the  head  "Esotropia." 

A  double  catatropia  complicated  by  a  plus  cyclotropia 
is  caused  by  the  inferior  recti  alone,  and  should  be  re- 
lieved by  a  division  of  the  temporal  and  central  fibers  of 
both  these  muscles.  If  in  such  a  case  there  is  want  of 


586        HYPERTROPIA  AND  CATATROPIA. 

converging  power,  this  would  be  helped  by  these  opera- 
tions; but  if  there  is  an  excess  of  convergence,  this  will 
be  made  greater.  How  to  deal  with  such  a  case  has 
been  set  forth  alread}-. 

The  most  common  form  of  vertical  heterotropia  is  hy- 
pertropia  of  one  eye  and  catatropia  of  the  other.  If 
there  is  no  complicating  cyclotropia,  the  first  operation 
should  be  a  central  partial  tenotomy  of  the  superior 
rectus  of  the  hypertropic  eye,  the  aim  being  to  accom- 
plish more  than  half  the  correction,  rather  than  less;  and 
the  second  operation,  after  from  two  to  four  weeks,  should 
be  a  central  partial  tenotomy  of  the  inferior  rectus  of  the 
catatropic  eye,  with  the  view  of  placing  the  visual  axes 
in  the  same  plane.  These  operations  will  result  only  in 
lessening  the  tension  of  the  muscles  that  are  too  strong. 
If  some  of  the  old  errors  should  remain,  the  third  opera- 
tion should  be  a  straight-forward  shortening  of  the  in- 
ferior rectus  of  the  hypertropic  eye.  These  three  oper- 
ations should  correct  the  most  aggravated  vertical  error; 
but  a  fourth  operation  could  be  done — viz.,  a  straight- 
forward shortening  of  the  superior  rectus  of  the  cata- 
tropic eye. 

Hypertropia  of  one  eye  and  catatropia  of  the  other, 
complicated  by  a  plus  cyclotropia,  should  be  corrected  by 
a  marginal  partial  tenotomy,  including  the  nasal  and 
central  fibers,  of  the  superior  rectus  of  the  hypertropic 


CYCLOTROPIA.  587 

eye;  and  a  marginal  partial  tenotomy,  including-  the 
temporal  and  central  fibers,  of  the  inferior  rectus  of  the 
catatropic  eye. 

Hypertropia  of  one  eye  and  catatropia  of  the  other, 
complicated  by  parallel  cyclotropia — plus  in  one  eye  and 
minus  in  the  other — would  require  one  method  of  pro- 
cedure if  the  hypertropic  eye  had  the  plus  cyclotropia, 
and  a  very  different  method  if  the  hypertropic  eye  had 
the  minus  cyclotropia.  In  the  former  case  the  marginal 
tenotomy  of  the  superior  rectus  of  the  hypertropic  eye 
should  include  the  nasal  and  central  fibers,  and  the 
marginal  tenotomy  of  the  inferior  rectus  of  the  cata- 
tropic eye  should  include  its  nasal  and  central  fibers; 
while  in  the  latter  case  the  tenotomy  would  include  the 
temporal  and  central  fibers  of  the  superior  rectus  of  the 
hypertropic  eye  and  the  temporal  and  central  fibers  of 
the  inferior  rectus  of  the  catatropic  eye. 

CYCLOTROPIA. 

Cyclotropia  is  an  actual  loss  of  parallelism  between 
the  vertical  axes  of  the  eyes  and  the  fixed  median  plane 
of  the  head.  This  condition  probably  never  exists  alone, 
though  it  is  often  found  in  connection  with  other  forms 
of  heterotropia,  as  has  been  shown  already.  It  may  be, 
however,  the  chief  condition  in  some  cases,  the  lateral  or 
vertical  deviations  of  the  visual  axes  being  complications; 


588  CYCLOTROPIA. 

but  far  more  often  the  cyclotropia  is  a  complication  of  the 
vertical  and  lateral  deviations. 

There  are  two  classes  of  cyclotropia — namely,  similar 
and  dissimilar.  In  the  former  class  the  cyclotropia  is 
plus  or  minus  in  both  eyes,  while  in  the  latter  class  the 
error  is  plus  in  one  eye  and  minus  in  the  other.  The 
former  might  be  termed  "non-parallel  cyclotropia" 
that  is,  the  vertical  axes  are  either  divergent  or  conver- 
gent; the  latter  might  be  termed  "  parallel  cyclotropia  " 
— that  is,  the  vertical  axes  are  inclined  one  toward,  and 
the  other  from,  the  median  plane.  Cases  of  parallel  cy- 
clotropia are  not  often  found;  and  of  the  non-parallel 
class,  plus  cyclotropia  is  far  more  common  than  minus 
cyclotropia. 

In  parallel  cyclotropia,  if  the  minus  error  is  in  the 
right  eye  and  the  superior  oblique  is  the  cause,  in  the 
sense  of  being  too  strong,  the  complication  for  that  eye 
will  be  catatropia;  but  if  the  superior  rectus  is  the  cause, 
the  complication  will  be  hypertropia.  The  plus  cyclo- 
tropia of  the  left  eye  will  be  complicated  with  hypertro- 
pia if  the  inferior  oblique  is  the  cause,  and  catatropia  will 
be  the  complication  if  the  inferior  rectus  is  the  cause. 
In  esotropia,  which  may  complicate  parallel  cyclotropia, 
the  internus  of  the  right  eye,  if  attached  too  high,  will 
aid  in  the  production  of  the  minus  cyclotropia,  and,  in 
some  cases,  may  be  the  chief  cause  of  the  minus  cyclo- 


CYCLOTROPIA.  589 

tropia;  while  the  internus  of  the  left  eye,  if  its  attach- 
ment is  too  low,  will  aid  in  the  production  of  the  left 
plus  cyclotropia.  A  too  low  right  externus  would  be  a 
causative  factor  of  the  minus  cyclotropia,  and  a  too  hig-h 
left  externus  would  help  to  cause  the  plus  cyclotropia  of 
this  eye. 

In  plus  cyclotropia  of  both  eyes,  the  error  is  caused  by 
both  inferior  obliques  or  by  both  inferior  recti.  If  the 
inferior  obliques  cause  the  error,  the  necessary  complica- 
tion will  be  double  hypertropia;  and  if  the  inferior  recti 
are  the  cause,  the  necessary  complication  will  be  double 
catatropia.  The  interni,  \vith  their  attachments  too  low, 
can  help  the  inferior  recti  in  the  development  of  plus  cy- 
clotropia; and  the  externi,  with  their  attachments  too 
high,  can  aid  the  inferior  obliques  in  the  causation  of  the 
plus  cyclotropia. 

Minus  cyclotropia  of  both  eyes  can  be  caused  by  the 
superior  obliques  alone,  when  the  complication  will  be 
double  catatropia;  it  can  also  be  caused  by  the  superior 
recti,  when  the  complication  will  be  double  hypertropia. 
Externi  that  are  too  low  can  help  the  superior  obliques 
in  the  production  of  minus  cyclotropia,  and  interni  that 
are  too  hig-h  can  aid  the  superior  recti  in  the  production 
of  minus  cyclotropia. 

Plus  cyclotropia  of  one  eye,  with  hypertropia,  is 
caused  by  the  inferior  oblique;  plus  cyclotropia  of  the 


590  CYCLOTROPIA. 

other  eye,  with  catatropia,  is  caused  by  the  inferior 
rectus. 

Cyclotropia,  of  whatever  kind,  can  be  detected  and 
measured  by  means  of  the  cyclo-phorometer,  used  as  in 
the  investigation  of  cyclophoria.  Because  of  the  am- 
blyopia  that  usually  exists  in  one  eye,  the  red  glass 
should  be  placed  in  the  cell  behind  the  rod  that  is  before 
the  better  eye.  The  prism  of  five  degrees  should  be 
placed  in  the  cell  behind  the  rod  that  is  in  front  of  the 
amblyopic  eye,  base  either  up  or  down — in  the  former 
position,  if  this  eye  is  hypertropic;  in  the  latter  position, 
if  it  is  catatropic.  If  the  red  streak  of  light  is  below, 
and  the  two  streaks  converge  at  the  ends  corresponding 
to  the  red  glass,  there  is  plus  cyclotropia;  if  they  con- 
verge at  the  other  ends,  there  is  minus  cyclotropia. 
Turning  the  rods  in  the  directions  that  will  parallel  the 
streaks,  and  at  the  same  time  make  them  appear  to  be 
horizontal,  measures  the  error;  and  the  pointing  of  the 
index  also  names  the  error.  If  the  two  stand  in  the  nasal 
quadrant,  the  error  is  plus;  if  they  stand  in  the  tem- 
poral quadrant,  the  error  is  minus. 

Cyclotropia,  like  the  other  forms  of  heterotropia,  is 
alternating — that  is,  the  fixing  eye,  whichever  it  may 
be,  will  have  its  vertical  axis  parallel  with  the  median 
plane  of  the  head,  while  the  vertical  axis  of  the  other 
eye  will  be  torted  out  or  in,  as  the  case  may  determine. 


CYCLOTROPIA.  591 

It  is  also  comitant,  the  angle  being-  the  same  in  all  posi- 
tions of  the  eyes. 

Cyclotropia,  caused  by  paralysis,  or  paresis,  and  oper- 
ations, is  non-comitant,  and  will  be  attended  by  most 
annoying-  symptoms.  The  symptoms  of  comitant  cyclo- 
tropia  are  those  common  to  the  other  forms  of  comitant 
heterotropia,  including-  the  loss  of  vision  in  one  eye, 
caused  by  mental  suppression.  Reflex  symptoms  are 
caused  by  nervous  tension  of  the  weaker  oblique  of  the 
fixing-  eye,  that  the  vertical  axis  may  be  made  parallel 
with  the  median  plane  of  the  head. 

TREATMENT  OF  CYCLOTROPIA. 

When  cyclotropia  is  a  complication  of  esotropia,  exo- 
tropia,  hypertropia,  and  catatropia,  it  should  be  treated 
as  has  been  set  forth  already.  Here  it  is  necessary  to 
speak  of  the  treatment  of  cyclotropia  when  it  is  the 
chief  error;  it  rarely  exists  alone.  If  there  is  much 
plus  cyclotropia,  complicated  by  double  h}'pertropia, 
but  no  marked  lateral  error  exists,  the  operative  effect 
should  be  equally  divided  between  the  two  eyes.  Either 
the  two  inferior  obliques  should  be  divided  completely 
(for  the  reason  that  a  partial  division  of  these  muscles 
seems  impossible)  with  the  Graefe  knife;  or  a  marginal 
tenotomy  of  both  superior  recti  should  be  done,  con- 
sisting- of  a  division  of  the  nasal  and  central  fibers  of 


592  CYCLOTROPIA. 

each,  leaving-  uncut  the  temporal  fibers.  The  results 
of  the  operation  on  the  superior  recti  would  be  the 
same  in  kind,  if  not  in  degree,  as  those  done  on  the  in- 
ferior obliques — namely,  the  two  eyes  would  be  partly, 
if  not  wholly,  relieved  of  the  outward  torsion,  and  they 
would  be  relieved  more  or  less  of  the  double  hypertropia. 
In  the  absence  of  any  lateral  deviation,  the  only  remain- 
ing muscles  to  be  subjected  to  operations  are  the  inferior 
recti,  whose  nasal  fibers  should  be  shortened  or  advanced 
equally.  The  operations  on  the  inferior  recti  would 
correct  more  or  less  of  the  plus  cyclotropia  and  the 
double  hypertropia. 

Plus  cyclotropia  complicated  by  hypertropia  of  the 
rig-tit  eye  and  catatropia  of  the  left  eye,  should  be  treated 
first  by  one  or  the  other  of  two  operations  on  the  rig-ht 
eye — that  is,  either  the  inferior  oblique  should  be  cut,  or 
a  marginal  partial  tenotomy,  including1  the  nasal  and 
central  fibers,  should  be  done  on  the  superior  rectus. 
Either  of  these  operations  would  correct  wholly  or  in 
part  both  the  plus  cyclotropia  and  the  hypertropia  of 
this  eye.  The  next  step  would  be  to  divide  the  temporal 
and  central  fibers  of  the  inferior  rectus  of  the  left  eye, 
which  would  correct  wholty  or  in  part  both  the  plus  cy- 
clotropia and  the  catatropia  of  this  eye.  If,  after  these 
operations  have  been  done,  there  should  remain  some  of 
both  the  plus  cyclotropia  and  the  hypertropia  of  the  rig-ht 


CYCLOTROPIA.  593 

eye  and  catatropia  of  the  left  eye,  one  other  operation 
should  be  done  on  each  eye — namely,  the  nasal  margin  of 
the  right  inferior  rectus  and  the  temporal  margin  of  the 
left  superior  rectus  should  be  either  shortened  or  ad- 
vanced. 

Plus  cyclotropia  uncomplicated  by  any  other  deviation, 
should  be  relieved  by  either  a  nasal  marginal  tenotomy 
of  both  superior  recti  or  by  a  nasal  marginal  advance- 
ment or  shortening  of  both  inferior  recti;  or,  in  cases  de- 
manding it,  both  operations  should  be  done  on  each  eye. 
Since  a  double  catatropia  would  result,  necessarily,  from 
either  marginal  tenotomies  of  the  superior  recti  or  mar- 
ginal shortenings  or  advancements  of  the  inferior  recti, 
the  former  operation  should  be  preferred,  for  the  reason 
that  it  is  both  more  easily  done  and  less  annoying  after- 
wards to  the  patient.  In  those  cases  in  which  sub-duction 
is  greater  than  normal  (more  than  three  degrees),  after 
the  nasal  marginal  tenotomies  of  the  superior  recti  have 
failed  to  correct  the  plus  cyclotropia,  temporal  marginal 
tenotomies  of  the  inferior  recti  should  take  the.  place  of 
the  nasal  marginal  shortenings  or  advancements. 

Minus  cyclotropia  complicated  or  uncomplicated  is  so 
rare  that  its  treatment  may  be  dismissed  with  the  state- 
ment that  the  part  of  a  superior  or  inferior  rectus  that 
should  be  cut  for  plus  cyclotropia  should  be  advanced  or 
shortened  for  a  minus  cyclotropia,  and  the  part  of  these 


594  CYCLOTROPIA. 

muscles  that  should  be  advanced  or  shortened  for  a  plus 
cyclotropia  should  be  cut  for  a  minus  cyclotropia.  The 
same  holds  true  also  as  to  operations  that  might  be  indi- 
cated on  the  lateral  recti,  when  errors  of  these  mus- 
cles complicate  minus  cyclotropia.  The  superior  oblique 
has  probably  never  been  divided,  nor  should  this  be  done, 
for  a  minus  cyclotropia. 

In  the  discussion  of  the  treatment  of  the  various  forms 
of  heterotropia,  much  has  been  taught  in  this  chapter 
that  cannot  be  appreciated  by  the  reader  who  is  not 
well  grounded  in  the  principles  set  forth  in  Chapter  I. 
In  this  department  of  ophthalmology  theory  directs 
practice  and  practice  sustains  theory.  Every  operation 
on  the  extrinsic  ocular  muscles  should  be  done  with  the 
view  of  enabling  the  superior  and  inferior  recti  to  plane 
the  visual  axes,  the  interni  and  externi  to  so  control 
these  axes  in  this  plane  as  to  make  them  intersect  at  the 
point  of  view,  and  the  obliques  to  parallel  the  vertical 
axes  of  the  eyes  with  the  median  plane  of  the  head.  In 
accomplishing  these  aims,  operations  should  be  so  done 
as  not  to  reduce  below  the  normal  the  duction  and  ver- 
sion power  of  a  single  muscle. 


CHAPTER   XL 


PARALYSIS  AND  PARESIS  OF   THE  OCULAR 

MUSCLES. 


A  BRIEF  review  of  the  nerve  supply  is  essential  to  a 
clear  understanding-  of  paralysis  or  paresis  affecting-  one 
or  more  of  the  ocular  muscles. 

THE  THIRD  NERVE  (mortor  oculi). — This  nerve  sends 
fibers  to  the  superior,  inferior,  and  internal  straight  mus- 
cles, and  to  the  inferior  oblique;  it  also  supplies  the 
muscle  that  elevates  the  upper  lid;  and  throug-h  the 
medium  of  the  ciliary  g-ang-lion  it  sends  fibers  to  the 
sphincter  of  the  iris  and  to  the  ciliary  muscle.  Its 
nucleus  of  origin  is  in  the  posterior  part  of  the  floor  of 
the  third  ventricle,  and  in  the  floor  of  the  aqueduct  of 
Sylvius.  There  is  a  nucleolus  of  origin  for  those  fibers 
of  this  nerve  that  finally  must  terminate  in  the  indi- 
vidual muscle  to  be  controlled  by  it.  Of  these  nucleoli 
the  most  anterior  one  is  connected  with  the  sphincter  of 
the  iris;  the  one  nearest  it  is  connected  with  the  ciliary 
muscle;  and  the  next  one,  in  order,  is  connected  with 
the  internal  rectus.  The  order  of  the  nucleoli  that  are 


(5951 


596  PARALYSIS   AND   PARESIS 

connected  with  the  other  muscles  supplied  by  the  third 
nerve  is  not  so  well  understood.  Some  optic  nerve 
fibers — these  doubtless  come  from  the  macula — are  con- 
nected with  the  nucleus  of  origin  of  the  oculo-mortor 
nerve,  and  thus  is  established  the  reflex  relationship 
between  the  retina  and  the  muscles  supplied  by  the 
third  nerve.  From  each  of  these  nucleoli,  fibers  go, 
through  the  internal  capsule,  to  higher  brain-centers, 
and  are  there  connected  with  fibers  from  nucleoli  in  the 
nucleus  of  origin  of  the  other  nerve  of  the  pair. 

To  illustrate:  The  first  conjugate  brain-center — the 
one  that  causes  both  superior  recti  to  rotate  the  eyes 
up — must  have  connected  with  it  fibers  that  come  from 
the  nucleolus  on  the  right  side,  which  is  connected  with 
the  right  superior  rectus,  and  the  nucleolus  on  the  left 
side,  which  is  connected  with  the  left  superior  rectus; 
likewise  the  nucleoli — the  one  on  the  one  side  of  the 
brain;  the  other,  on  the  other  side — connected  with 
their  respective  internal  recti,  must  each  send  fibers  to 
the  third  conjugate  brain  center  (the  center  of  conver- 
gence). Thus  the  connection  of  all  the  conjugate  brain- 
centers  with  corresponding  nucleoli  at  the  base  of  the 
brain  might  be  traced.  It  appears  evident  that  some 
of  these  connecting  fibers,  on  their  way  to  the  higher 
centers — the  conjugate  centers — must  cross  from  one 
side  of  the  brain  to  the  other. 


OF    THE   OCULAR    MUSCLES.  597 

THE  FOURTH  NERVE. — This  supplies  only  one  mus- 
cle, the  superior  oblique.  Its  nucleus  of  origin  is  im- 
mediately behind  that  of  the  third  nerve.  With  this 
nucleus  there  is  connected,  most  likely,  some  optic  nerve 
fibers,  to  establish  the  reflex  relationship  between  the 
retina  and  the  superior  oblique.  From  these  nuclei— 
the  one  on  the  one  side  of  the  brain;  the  other,  on  the 
other  side — fibers  must  go  to  form  a  common  connection 
with  the  sixth  conjugate  brain-center;  and  from  the 
right  nucleus,  fibers  must  go  to  form  a  common  connec- 
tion, in  the  eighth  conjugate  brain-center,  with  fibers 
from  the  nucleolus  controlling  the  left  inferior  oblique; 
likewise  fibers  must  go  from  the  nucleus  for  the  fourth 
nerve  on  the  left  side  to  connect,  in  the  ninth  conjugate 
center,  with  fibers  from  the  nucleolus  on  the  right  side 
that  controls  the  right  inferior  oblique.  Again,  it  is 
evident  that,  to  reach  these  conjugate  centers,  some 
fibers  must  cross  from  one  side  of  the  brain  to  the  other. 

THE  SIXTH  NERVE. — This  supplies  only  one  muscle, 
the  external  rectus  of  the  corresponding  side.  This 
nucleus  is  behind  that  of  the  fourth  nerve,  and  is  sepa- 
rated from  it  by  the  nucleus  of  origin  of  the  fifth  nerve. 
Fibers  from  the  nucleus  controlling  the  right  externus 
must  go  to  the  fourth  conjugate  brain-center,  to  connect 
with  fibers  from  the  nucleolus  that  controls  the  left  in- 
ternus;  and,  in  like  manner,  fibers  from  the  nucleus  that 


598  PARALYSIS   AND    PARESIS 

controls  the  left  externus  must  connect,  in  the  fifth  con- 
jugate brain-center,  with  fibers  from  the  nucleolus  that 
controls  the  right  internus.  Again,  it  appears  that  some 
fibers  must  cross  from  one  side  of  the  brain  to  the  other, 
that  these  connections  ma}*  be  formed.  It  is  reasonable 
to  suppose  that  some  optic  nerve  fibers  are  also  con- 
nected with  the  nucleus  of  the  sixth  nerve,  to  establish 
the  reflex  relationship  between  the  retina  and  the  ex- 
ternus. 

CAUSES. — Paralytic  or  paretic  heterotropia  may  be 
caused  by  disease  or  injury  of  the  muscle,  or  muscles, 
affected;  by  disease  or  injury  involving  the  nerve  trunk; 
by  disease  of  the  nucleus  at  the  base  of  the  brain;  by  dis- 
ease in  the  internal  capsule  or  corona  radiata;  and  by  dis- 
ease or  injury  of  a  conjugate  brain-center  in  the  cortex. 

Occasionally  children  are  born  with  paralysis  of  one 
or  more  ocular  muscles. 

The  disease  that  most  often  causes  paralysis  or  pare- 
sis of  the  ocular  muscles  is  syphilis.  The  muscles  most 
frequent!}*  involved,  when  syphilis  is  the  cause,  are  those 
supplied  by  the  third  nerve;  but  the  superior  oblique 
and  the  external  rectus  may  suffer  from  the  same  cause. 
The  history  of  the  case  will  show  whether  syphilis  is 
the  probable  cause.  Ocular  paralysis  is  one  of  the  re- 
mote results  of  syphilitic  infection. 

Rheumatism  affecting  the  muscle  itself  or  involving 


OF    THE    OCULAR    MUSCLES.  599 

the  nerve  in  its  course  is  not  infrequently  the  cause  of 
ocular  paralysis  or  paresis.  The  external  rectus  is  the 
muscle  that  most  frequently  suffers  from  this  cause. 

A  cold  contracted  from  undue  exposure  to  dampness, 
to  a  draught,  or  any  other  causative  agent,  may  cause, 
in  some  inexplicable  way,  paresis  or  even  paralysis  of 
any  one  of  the  ocular  muscles. 

Tumor,  or  other  disease  of  the  internal  capsule  and 
the  corona  radiata,  will  cause  paralysis  of  conjugate 
'movements,  but  not  paralysis  of  the  muscles  ;  duction 
power,  which  is  reflex  in  character,  will  not  be  involved, 
but  the  verting  power,  which  is  volitional,  will  be  im- 
paired or  lost.  In  such  cases,  symptoms  referable  to 
other  parts  are  always  associated  with  the  eye  symp- 
toms. 

Injury  or  disease  of  the  cortex,  involving  an}-  one  of 
the  nine  conjugate  centers,  will  result  in  paralysis  or 
paresis  of  one  muscle  connected  with  each  eye;  but  the 
paralysis  will  show  itself  in  the  absence  of  verting 
power,  with  no  loss  of  duction  power.  To  illustrate:  If 
the  third  conjugate  center  alone  is  involved,  there  can 
be  no  convergence,  but  because  of  freedom  from  disease 
of  the  fourth  and  fifth  conjugate  centers  the  two  eves 
can  be  made  to  turn  harmoniously  to  the  right  or  to  the 
left;  and  adduction,  which  is  reflex,  will  be  unimpaired. 

Disease   or  injury  of   the   orbit   involving    tbe   parts 


600  PARALYSIS   AND    PARESIS 

around  the  sphenoidal  fissure,  disease  in  the  orbital 
cavity  behind  the  eye,  and  disease  or  injury  of  the  mus- 
cles themselves,  can  cause  paralysis  of  any  one  or  sev- 
eral of  the  orbital  muscles. 

INDIVIDUAL  FORMS  OF  PARALYSIS. 

(1)  THE  THIRD  NERVE. — If  the  cause  is  in  the  nu- 
cleus or  in  the  course  of  the  nerve  before  it  divides  into 
its  several  branches,  the  following-  conditions  will  be 
present:  («)  Ptosis;  (b)  the  eye  will  be  turned  out  more 
or  less  by  the  unopposed  externus,  and  it  cannot  be 
rotated  in;  (c)  the  eye  will  be  turned  slightly  down  and 
will  be  torted  in  by  the  unopposed  superior  oblique;  the 
eye  cannot  be  turned  upward,  for  both  elevators — the 
superior  rectus  and  the  inferior  oblique — are  involved, 
and  it  can  be  turned  downward  only  slightly  by  the 
superior  oblique,  for  the  chief  depressor — the  inferior 
rectus — is  powerless;  (d)  the  pupil  will  be  dilated  and 
the  accommodation  will  be  suspended.  There  will  be 
neither  headache,  nausea,  nor  dizziness;  for  the  fallen 
lid  cuts  off  the  light  from  the  eye,  and  the  brain-cen- 
ters— the  fusional  centers — are  not  excited. 

If  the  disease  involves  only  one  branch  after  it  leaves 
the  main  nerve,  only  one  muscle  will  be  affected.  If  the 
diseased  branch  is  the  one  supplying  the  muscle  that 
elevates  the  upper  lid,  the  only  symptom  will  be  ptosis. 


OF    THE    OCULAR   MUSCLES.  601 

If  the  involved  branch  is  the  one  supplying1  the  internus, 
both  adduction  and  adversion  \vill  be  impaired  or  abol- 
ished, the  eye  being-  turned  out;  and  because  of  the  ab- 
sence of  ptosis  there  will  be  crossed  diplopia,  associated 
with  headache,  nausea,  and  dizziness,  due  to  excitation  of 
brain-centers.  If  the  affected  branch  is  the  one  supply- 
ing- the  inferior  rectus,  sub-duction  will  be  impaired  or 
absent,  and  sub-version  by  the  superior  oblique  will  be 
only  slig-ht;  and,  for  the  same  reason  g-iven  above,  there 
will  be  diplopia  in  the  lower  field,  headache,  nausea,  and 
dizziness.  If  the  involved  branch  is  the  one  supplying- 
the  superior  rectus,  superduction  will  be  impaired  or 
lost,  and  superversion  by  the  inferior  oblique  will  be  only 
slig-ht;  and  there  would  be  diplopia  in  the  upper  field, 
headache,  nausea,  and  dizziness.  If  the  branch  affected 
is  the  one  supplying1  the  inferior  oblique,  superduction 
(by  the  superior  rectus)  will  probably  be  unimpaired, 
and  superversion  will  be  only  slightly  lessened;  and  there 
will  be  diplopia  in  the  upper  field,  headache,  nausea, 
and  dizziness  on  attempting-  to  look  up,  as  would  be 
true,  also,  when  the  superior  rectus  is  paretic.  The 
symptoms  caused  by  paresis  of  the  inferior  rectus  (and 
by  paresis  of  the  superior  oblique,  as  will  be  shown  later) 
are  always  more  pronounced,  for  the  reason  that  we  look 
down  more  than  we  look  up.  If  the  branch  implicated  is 
the  one  going  to  the  ciliary  g-ang-lion,  thence  to  the 


602  PARALYSIS    AND    PARESIS 

ciliary  muscle  and  the  sphincter  of  the  iris,  there  will 
be  complete  loss  of  accommodation  and  full  dilatation  of 
the  pupil ;  but  if  the  ciliary  ganglion  itself  is  the  involved 
part,  there  will  be  complete  loss  of  accommodation,  but 
the  pupil  will  not  be  fully  dilated.  Both  the  sphincter  of 
the  iris  and  the  dilator  fibers  will  be  paralyzed,  hence 
partial  dilatation,  but  complete  inactivity  of  the  pupil. 
The  symptoms  will  be:  Dread  of  light,  inability  to  see 
near  objects  well,  and  pain  referable  to  the  eye. 

(2)  THE  FOURTH  NERVE. — Since  this  nerve  supplies 
only  the  superior  oblique,  the  symptoms  are  the  same, 
whether  the  disease  is  at  the  nucleus  of  origin,  or  in 
the  course,  of  the  nerve.     The  eye  is  torted  out  by  the 
unopposed  inferior  oblique  ;   sub-version  is  limited,  but 
sub-duction  is  probably  not  much  impaired.     There  is 
always  diplopia  in  the  lower   field.     Nausea,  vomiting, 
dizziness,  and  headache  are  nearly  always  pronounced. 

(3)  THE   SIXTH  NERVE. — Since  this  nerve  supplies 
only  the  external  rectus,  the  symptoms  are  alwa}Ts  the 
same,   whether   it   is  diseased  at  its  nucleus  or   in    its 
course.     The  eye  will  be  turned  in,  and  both  abduction 
and  ab version  will  be  abolished.     There  will  be  homony- 
mous  diplopia.     There  being  no  ptosis  to  cut  off  light 
from  the  affected  eye,  the  cortical  centers  will  become 
excited,  and  there  will  be  headache,  nausea,  and  dizziness 
when  attempting  to  look  toward  the  corresponding  side. 


OP    THE    OCULAR    MUSCLES.  603 

It  is  only  when  there  is  extensive  disease  at  the  base 
of  the  brain,  or  disease  involving-  all  the  structures  in 
the  sphenoidal  fissure,  or  extensive  disease  in  the  orbit 
itself,  that  paralysis  of  all  the  muscles  of  one  eye  is 
possible.  The  symptoms  of  such  a  condition  \vould  be 
immobility  of  the  eye  in  any  direction;  protrusion  of  the 
eye,  even  when  the  disease  causing*  it  is  not  in  the  orbit, 
for  there  would  be  relaxation  of  all  the  external  muscles; 
diplopia  would  be  pronounced  in  all  directions  (unless 
the  optic  nerve  has  been  involved  in  the  disease  process 
within  the  cranium),  were  it  .not  for  the  fact  that  the 
upper  lid  usually  falls  far  enough  down  to  cover  the 
pupil;  the  ptosis  would  be  complete,  were  it  not  modified 
by  the  protrusion  of  the  globe;  and,  finally,  the  accom- 
modation would  be  suspended  and  the  pupil  dilated.  An 
ophthalmoplegia  externa,  without  associated  parahrsis  of 
the  ciliary  muscle  and  sphincter  of  the  iris,  is  incon- 
ceivable, and  that,  too,  whether  the  disease  causing  it  is 
intracranial  or  intraorbital.  On  the  contrary,  paralysis 
of  the  muscles  within  the  eye  may  be  unassociated  with 
paralysis  of  the  external  muscles. 

DIAGNOSIS. — There  can  never  be  any  doubt  as  to  what 
rectus  muscle  is  involved  when  the  paralysis  is  complete; 
but  when  there  is  paresis,  it  is  often  a  difficult  matter 
to  determine  to  which  eye  the  affected  muscle  belongs 
and  what  muscle  is  involved,  for  in  some  of  these  cases 


604  PARALYSIS    AND    PARESIS 

there  is  no  perceptible  squint,  and  apparently  no  limita- 
tion of  movement.  The  unfailing-  test  for  paresis  and 
(were  it  necessary)  for  paralysis  is  the  diplopia  test. 
This  test  will  always  be  responded  to  in  the  direction  of 
action  of  the  affected  muscle,  and  it  invariably  deter- 
mines the  eye  to  which  the  affected  muscle  belongs 
and  unerringly  points  to  the  paretic  muscle.  For  the 
laterally  acting-  muscles  the  following-  rule  may  be  formu- 
lated: The  candle  will  appear  sing-le  in  the  left  field  if 
the  affected  muscle  is  a  right  vertor,  but  will  be  doubled 
in  the  right  field,  and  vice  versa  if  the  affected  muscle 
is  a  left  vertor;  the  eye  to  'which  the  affected  muscle  be- 
longs will  see  the  candle  that  is  farthest  removed  {the 
false  candle},  and  the  affected  muscle  is  on  that  side  of 
this  eye  corresponding"  to  the  direction  of  doubling-.  If 
the  doubling  is  to  the  right,  the  paretic  muscle  is  a  right 
vertor,  and  is,  therefore,  either  the  right  externus  or  the 
left  internus.  If  the  right  eye  sees  the  candle  farthest 
removed,  it  is  the  right  externus;  but  if  the  left  eye 
sees  the  false  light,  it  is  the  left  internus.  Nothing 
could  be  more  easily  accomplished  than  the  complete 
diagnosis  of  paresis  of  a  right  vertor  or  a  left  vertor. 

Although  there  are  two  sub-vertors  and  two  super- 
vertors  for  each  eye,  the  determination  of  the  question, 
"To  which  eye  belongs  the  paretic  muscle?"  is  as  easy 
as  can  be;  and  the  difficulty  in  the  way  of  finding  the 


OF    THE    OCULAR   MUSCLES.  605 

involved  muscle  is  only  apparent.  If  the  affected  mus- 
cle is  a  sub-vertor,  the  candle  will  appear  single  above, 
but  double  below,  the  horizontal  plane,  and  vice  versa 
if  the  affected  muscle  is  a  supervertor.  The  following 
is  the  rule  for  finding-  the  eye  to  which  the  affected 
muscle  belongs  and  for  locating1  the  paretic  muscle:  The 
eye  to  "which  the  paretic  sub-vertor  or  supervertor  be- 
longs sees  the  candle  that  is  farthest  removed  (cither 
above  or  belovS)  from  the  horizontal  plane,  and  the 
direction  of  the  leaning'  of  the  false  candle  determines 
"whether  it  is  a  straig-ht  or  an  oblique  muscle  that  is 
involved.  If  the  doubling-  is  below  the  horizontal 
plane  and  the  false  candle  leans  toward  the  same  side, 
the  inferior  rectus  is  the  paretic  muscle;  if  it  leans 
toward  the  opposite  side,  the  superior  oblique  is  the 
paretic  muscle;  but  if  the  doubling  is  above  the  hori- 
zontal 'plane  and  the  false  candle  leans  toward  the 
corresponding-  side,  the  inferior  oblique  is  paretic;  if  it 
leans  toward  the  opposite  side,  the  superior  rectus  is 
paretic. 

The  accompanying-  cuts  illustrate  perfectly  the  rules 
g-iven  above.  In  the  cuts  illustrating-  paresis  and  paraly- 
sis of  the  right  and  left  vertors,  the  doubling-  is  repre- 
sented as  existing"  when  the  vertical  plane  has  been 
reached,  the  distance  between  the  false  and  the  true 
candles  increasing  as  the  candle  is  carried  farther  in  the 


606 


PARALYSIS    AND    PARESIS 


direction  of  action  of  the  affected  muscle.  This  is  always 
true  in  paralysis,  but  in  paresis  the  doubling'  may  not 
occur,  in  passing-  from  the  field  of  fusion  into  the  field  of 
diplopia,  until  the  vertical  plane  has  been  passed.  Like- 
wise, in  the  cuts  representing  paralysis  and  paresis  of 
the  sub-vertors  and  supervertors,  the  doubling-  is  repre- 
sented as  having-  occurred  before  reaching-  the  horizontal 
plane,  in  passing-  from  the  fusion  field  into  the  field  of 
diplopia. 


a         -f 

A   -A 


Fig-  79- 


Fig-.  79  illustrates  paralysis  or  paresis  of  a  right 
vertor,  either  the  rig-ht  externus  or  the  left  internus. 
If  the  rig-ht  eye  sees  candle  b,  the  affected  muscle  is 
the  right  externus;  but  if  the  left  eye  sees  candle  b,  the 
affected  muscle  is  the  left  internus.  A  red  glass  before 
either  eye  shows  quickly  which  eye  it  is  that  sees  the 
false  candle;  covering  either  eye  with  a  card  will  also 
show  which  eye  it  is  that  sees  candle  b. 

The  false  candle  may  be  above  or  below  the  true,  or 
of  the  same  height  as  shown  in  the  cut,  depending  on 
the  state  of  imbalance  or  balance  of  the  vertically  acting 


OF    THE    OCULAR    MUSCLES.  607 

muscles.  A  leaning  of  the  false  candle  will  appear 
whenever  there  is  a  cyclophoria. 

Fig.  80  illustrates  paralysis  or  paresis  of  a  left  vertor, 
either  the  left  externus  or  the  right  internus.  If  the  left 
eye  sees  candle  b,  the  affected  muscle  is  the  left  externus; 
but  if  the  right  eye  sees  candle  b,  it  is  the  right  internus. 

The  false  candle  in  paralysis  of  a  right  or  a  left 
vertor  is  not  always  parallel  with  the  true  candle. 
When  this  is  true,  the  direct  antagonist  of  the  paralyzed 


Fig.  80. 

muscle  has  not  an  ideal  attachment  to  the  globe;  its  at- 
tachment is  either  too  high  or  too  low.  When  the  healthy 
muscle  is  an  internus,  if  the  false  candle  leans  toward 
the  side  of  the  affected  eye,  its  attachment  is  too  high, 
or  there  is  minus  cyclophoria ;  but  if  the  false  candle 
leans  toward  the  opposite  side,  its  attachment  is  too  low, 
or  there  is  a  plus  cyclophoria.  Just  the  opposite  is  true 
when  the  healthy  muscle  is  an  externus. 

The  false  candle  may  be  higher  or  lower  than,  or 
even  with,  the  true,  depending  on  the  state  of  imbalance 
or  balance  of  the  vertically  acting  muscles. 


608 


PARALYSIS    AND    PARESIS 


# 


Fig.  81. 


Fig.  81  and  Fig.  82  illustrate  paralysis 
of  a  sub-vertor  muscle  of  either  one  eye  or 
the  other.  Below,  in  parallel  columns, 
will  be  shown  the  significance  of  each  cut. 
Inclination  toward  the  opposite  side  points 
to  the  superior  oblique,  while  inclination 
toward  the  same  side  points  to  the  inferior 
rectus: 

Fig.  82  is  illus- 
trative of  paralysis 
of  either  the  supe- 
rior oblique  or  the 
inferior  rectus  of 
the  eye  that  sees 


Fig.  81  is  illus- 
trative of  paralysis 
of  either  the  supe- 
rior oblique  or  the 
inferior  rectus  of 
the  eye  that  sees 
candle  b.  If  the 
right  eye  sees  it, 
the  affected  muscle 
is  the  inferior  rec- 
tus; but  if  the  left 
eye  sees  it,  the  af- 
fected muscle  is  the  supe- 
rior oblique. 


candle  b.  If  the 
right  eye  sees  it, 
the  affected  muscle 
is  the  superior  ob- 
lique; but  if  the 
left  eye  sees  it,  the 
affected  muscle  is 
ferior  rectus. 


0 

D 


* 

^ 
r 


* 


Fig.  82. 

the  in- 


In  either  case  the  false  candle  may  be  to  the  right  or 
left  of  the  true,  depending  on  the  relationship  between 
the  lateral  recti  muscles. 


OF    THE   OCULAR    MUSCLES. 


609 


4 


Fig.  83  and  Fig.  84  illustrate  paralysis 
of  a  supervertor  muscle  of  either  one  eye 
>  \      or  the  other.     Below,  in  parallel  columns,      / 
\J    will  be  shown  the  significance  of  each  cut.   ;[J 
&     Inclination  toward  the  opposite  side  points 
to  the  superior  rectus,  while  inclination  to- 
ward the  same  side  points  to  the  inferior 


oblique: 

Fig.  83  is   illus- 
trative of  paralysis 
of  either  the  supe- 
rior rectus   or  the 
inferior  oblique  of 
the  eye  that  sees 
candle  b.     If  the 
right   eye  sees  it, 
the  affected  mus- 
cle is  the  superior 
rectus;   but  if   the 
Fig- 83'    left  eye  sees  it,  the 
affected  muscle  is  the  in- 
ferior oblique. 


Fig.  84  is  illus- 
trative of  paralysis 
of  either  the  supe- 
rior rectus  or  the 
inferior  oblique  of 
the  eye  that  sees 
candle  b.  If  the 
right  eye  sees  it, 
the  affected  mus- 
cle is  the  inferior 
oblique;  but  if  the 
left  eye  sees  it,  the 
affected  muscle  is  the  su- 
perior rectus. 


Fig.  84. 


As  in  paresis  or  paralysis  of  the  sub-vertors,  the  false 
candle  may  be  to  the  right  or  left  of  the  true,  depending 
on  the  relative  strength  of  the  laterally  acting  muscles. 


610  PARALYSIS   AND    PARESIS 

In  making  a  diagnosis  of  paralysis  or  paresis  of  the 
ocular  muscles,  by  means  of  the  diplopia  test,  the  candle 
need  be  carried  only  in  the  four  cardinal  directions — that 
is,  the  head  should  be  erect;  and  in  testing-  for  paresis  of 
the  right  and  left  vertors,  the  candle  should  be  carried 
only  along  the  extended  horizontal  plane  of  the  head  di- 
rectly to  the  right  and  left  of  the  vertical  plane;  and  in 
testing  for  paresis  of  the  sub-vertors  and  supervertors, 
the  candle  should  be  carried  only  in  the  extended  median 
plane  of  the  head,  above  and  below  the  horizontal  plane. 

For  detecting  paralysis  or  paresis  of  the  sub-vertors 
and  supervertors,  nothing  serves  better  than  a  horizontal 
line  at  a  distance  of  twenty  feet.  If  the  sub-vertors  are 
at  fault,  elevating  the  head,  while  still  looking  at  the 
line,  will  cause  it  to  double,  the  false  line  appearing  be- 
low the  true.  If  the  false  line  leans  toward  the  corre- 
sponding side,  the  affected  muscle  is  the  inferior  rectus; 
but  if  it  leans  toward  the  opposite  side,  the  affected  mus- 
cle is  the  superior  oblique. 

When  a  right  vertor  or  a  left  vertor  is  paralyzed,  the 
resulting  deviation  might  be  mistaken  for  comitant  lat- 
eral heterotropia.  This  may  be  avoided  in  two  ways 
—first,  by  a  test  of  the  verting  power,  when  the  affected 
eye  will  always  lag  behind  its  fellow  if  the  two  eyes  are 
turned  in  the  direction  of  action  of  the  paretic  muscle, 
whereas,  in  comitant  squint,  the  deviating  eye  moves 


OF    THE    OCULAR   MUSCLES.  611 

always  through  as  great  an  arc  as  the  fixing-  eye;  sec- 
ondly, by  covering1  the  eyes  alternately,  the  secondary 
deviation  will  always  be  greater  than  the  primary,  when 
there  is  paralysis.  But  in  comitant  squint  the  secondary 
and  the  primary  deviations  are  always  the  same. 

In  paralytic  squint  there  is  always  diplopia  in  one 
part  of  the  field,  with  binocular  sing-le  vision  in  the  op- 
posite part;  while  in  comitant  squint  there  is  no  diplo- 
pia in  any  part  of  the  field. 

A  very  good  diagnostic  feature  is  the  pose  of  the  head 
in  cases  of  paralysis  of  an  orbital  muscle.  In  paralysis 
of  a  lateral  rectus  muscle,  the  face  is  always  turned  in 
the  direction  of  action  of  the  affected  muscle — that  is, 
if  a  left  vertor  is  paralyzed,  the  face  will  be  turned  to 
the  left  in  the  interest  of  binocular  single  vision,  and 
vice  versa  if  a  right  vertor  is  paralyzed;  if  a  sub-vertor 
is  paralyzed,  the  face  will  be  depressed;  and  if  a  super- 
vertor  is  paralyzed,  the  face  will  be  elevated. 

In  "paralysis  of  motion,  rather  than  of  muscle,"  duc- 
tion  power,  which  is  reflex  in  the  sense  that  it  is  not  vo- 
litional, is  not  involved.  This  statement  covers  all  the 
conjugate  brain-centers  from  the  first  to  the  fifth,  inclu- 
sive— those  centers  that  are  concerned  with  the  recti 
muscles.  Since  there  is  no  voluntary  action  of  the  ob- 
liques, the  cortical  centers  (if  there  be  such)  governing 
them  must  act  independently  of  the  will.  These  centers 


612  PARALYSIS   AND   PARESIS 

are  the  sixth,  seventh,  eighth,  and  ninth.  That  these 
conjugate  centers  for  the  obliques  may  be  involved  in 
pathologic  changes  must  be  conceded  Since  the  object  of 
the  sixth  and  seventh  centers  is  to  prevent  diplopia,  on 
looking  down  and  up,  respectively,  these  correspond  per- 
fectly in  action  with  the  reflex  centers  of  the  recti  that 
are  also  concerned  with  the  prevention  of  diplopia  when 
images  are  displaced  by  prisms;  therefore  they  ought  not 
to  be  affected  in  disease  of  the  cortex.  The  eighth  and 
ninth  centers  are  not  concerned  with  the  prevention  of 
diplopia;  but,  what  is  probably  of  as  much  importance, 
they  are  concerned  with  the  steadying  of  all  objects  in 
the  field  of  vision  whenever  the  eyes  are  voluntarily 
moved  in  an  oblique  direction.  For  instance,  when  the 
gaze  is  directed  up  and  to  the  right,  or  down  and  to 
the  left,  the  eyes  would  be  torted  to  the  right,  were  it 
not  for  the  eighth  conjugate  center,  when  all  objects 
would  be  made  to  appear  to  incline  to  the  left  from  their 
real  position,  their  inclination  corresponding  precisely 
with  the  degree  of  torsioning.  This  is  prevented  by 
the  eighth  conjugate  center,  which  maintains  the  paral- 
lelism between  the  vertical  axes  of  the  eyes  and  the  me- 
dian plane  of  the  head  in  such  a  voluntary  rotation.  It 
appears,  therefore,  that  disease  of  this  center  would  be 
attended  by  a  wheel-like  movement  of  objects  whenever 
the  visual  axes  are  made  to  move  up  and  to  the  right,  or 


OF    THE    OCULAR    MUSCLES.  613 

down  and  to  the  left,  which  appearance  would  not  be  if 
the  gaze  were  directed  up  and  to  the  left,  or  down  and 
to  the  right.  But  if  the  ninth  conjugate  center  were  in- 
volved in  pathologic  change,  the  wheel-like  movement  of 
objects  would  be  observed  only  when  the  gaze  is  up  and 
to  the  left,  or  down  and  to  the  right.  In  neither  case 
would  there  be  diplopia. 

Should  the  sixth  conjugate  center  be  involved,  on  look- 
ing down  at  a  candle  it  would  appear  double,  the  one 
seen  by  the  right  eye  leaning  to  the  left  and  the  one  seen 
by  the  left  eye  leaning  to  the  right;  the  diplopia  would 
be  attended  by  dizziness  and  nausea.  In  the  upper  field 
there  would  be  no  diplopia. 

Should  the  seventh  conjugate  center  become  diseased, 
the  diplopia  would  be  in  the  upper  field,  and  the  candle 
seen  by  the  right  eye  would  lean  to  the  right,  and  the 
one  seen  by  the  left  eye  would  incline  to  the  left.  It  ap- 
pears that  each  oblique  muscle  is  connected  by  individual 
nerve  fibers  with  three  centers — one  center,  basal;  the 
two  others,  probably  cortical.  The  former  center  has 
connected  with  it  fibers  from  only  one  muscle,  but  each 
of  the  latter  has  connected  with  it  fibers  from  two  ob- 
lique muscles,  one  of  these  belonging  to  one  eye  and  the 
other  to  the  other  eye;  and,  therefore,  they  are  conjugate 
centers.  All  the  fibers  from  these  three  centers  come 
together  and  form  the  trunk  of  the  nerve,  a  disease  of 


614  PARALYSIS   AND   PARESIS 

which  suspends  the  independent  and  conjugate  action  of 
the  muscle  supplied  by  it;  and  the  muscles  of  the  fellow 
eye  are  not  involved.  The  right  superior  oblique  is  con- 
nected with  the  sixth  conjugate  center,  as  is  also  the  left 
superior  oblique;  the  right  superior  oblique  is  also  con- 
nected with  the  eighth  conjugate  center,  as  is  also  the 
left  inferior  oblique.  Disease  of  the  sixth  center,  as  al- 
ready shown,  gives  trouble  only  when  looking  directly 
down;  disease  of  the  eighth  center  causes  trouble,  as 
shown  above,  only  when  looking  up  and  to  the  right,  or 
down  and  to  the  left.  Disease  of  these  two  conjugate 
centers  would  have  no  influence  over  the  basal  center 
that  gives  duction  or  fusion  power  to  either  of  the  two 
muscles  mentioned — that  power  that  is  exercised  when 
images  are  displaced  by  oblique  astigmatism,  natural  or 
artificial. 

Each  internus  muscle  is  also  connected  with  three  cen- 
ters— one  center,  basal;  the  two  others,  cortical.  The  for- 
mer is  reflex;  the  latter,  volitional.  To  illustrate:  The 
right  internus  has  its  reflex  center — the  center  giving  it 
duction  or  fusion  power — in  the  nucleus  of  the  mortor 
oculi;  it  is  also  connected  with  the  third  conjugate  brain- 
center,  as  is  also  the  left  internus;  it  is  also  connected 
with  the  fifth  conjugate  center,  as  is  also  the  left  exter- 
nus.  All  the  fibers  from  these  three  centers  for  the  right 
internus  form  the  bundle  that  constitutes  the  branch  of 


OF    THE    OCULAR   MUSCLES.  615 

the  third  nerve,  supplying  it  with  its  threefold  power. 
Disease  of  this  branch  suspends  both  the  reflex  (fusion) 
and  voluntary  power  of  this  muscle;  it  can  neither  ad- 
duct,  converge,  nor  advert  the  eye  to  which  it  belongs. 
Disease  of  the  third  conjugate  center  involves  only  those 
fibers  that  convey  to  the  muscle  the  convergence  impulse; 
disease  of  the  fifth  conjugate  center  involves  only  those 
fibers  that  convey  the  adversion  impulse;  likewise  dis- 
ease of  the  reflex  nucleolus  involves  only  those  fibers 
that  convey  the  fusion  impulse.  Disease  of  the  third 
conjugate  center  would  suspend,  of  course,  the  conver- 
ging power  of  the  left  internus  also;  while  disease  of  the 
fifth  conjugate  center  would  affect  the  abverting  power 
of  the  left  externus  as  well  as  the  adverting  power  of 
the  right  internus.  Thus  each  muscle,  with  its  several 
centers,  might  be  studied. 

It  only  remains  to  speak  of  the  symptoms  that  would 
present  themselves,  should  any  one  of  the  five  conjugate 
centers,  controlling  the  recti,  become  diseased: 

(1)  Disease  of  the   first   conjugate  center:    inability  to 

supervert  the  eyes,  but  no  diplopia. 

(2)  Disease  of  the  second  conjugate  center:  inability  to 

sub-vert  the  eyes,  but  no  diplopia. 

(3)  Disease  of  the  third  conjugate  center:    inability  to 

converge  the  eyes,  with  diplopia  in  the  near. 


616  PARALYSIS   AND   PARESIS 

(4)  Disease  of  the  fourth  conjugate  center:  inability  to 

rotate  the  eyes  to  the  right,  either  cardinally  or 
obliquely,  but  no  diplopia. 

(5)  Disease  of  the  fifth  conjugate  center:    inability  to 

rotate  the  eyes  to  the  left,  either  cardinally  or 
obliquely,  but  no  diplopia. 

TREATMENT. 

In  any  form  of  paralysis  of  muscle — that  is,  when  the 
disease  causing  it  is  below  the  internal  capsule — the 
diplopia  should  be  prevented  by  covering  the  affected 
eye,  which  will  relieve  all  nervous  symptoms,  such  as 
headache,  dizziness,  and  nausea.  The  affected  eye 
should  be  kept  under  cover  until  the  disease  has  been 
cured.  In  paralysis  of  the  third  nerve,  nature  supplies 
the  cover  in  the  production  of  ptosis,  and  usually  the 
last  muscle,  supplied  by  the  third  nerve,  to  regain  its 
power  is  the  elevator  of  the  upper  lid.  If  any  case  is 
clearly  rheumatic,  it  should  be  treated  with  large  doses 
of  the  salicylate  of  sodium  or  other  anti-rheumatic  rem- 
edy; if  the  cause  is  syphilis,  iodide  of  potassium  in  in- 
creasingly large  doses  should  be  given  after  meals;  if 
the  cause  is  not  known,  the  case  should  be  treated  with 
the  iodide  of  potassium.  Early  in  any  case  the  admin- 
istration of  the  fluid  extract  of  jaborandi,  in  doses  of 
twenty  drops  at  9  A.M.,  3  P.M.,  and  9  P.M.,  by  pro- 


OF    THE   OCULAR    MUSCLES.  617 

moting  absorption  of  effused  serum,  will  greatly  aid  the 
iodides  in  the  work  of  hastening-  the  absorption  of  plas- 
tic effusion.  Bichloride  of  mercury  in  small  doses  may 
also  be  given. 

The  above  remedies  should  be  continued  until  the 
diplopia  has  entirely  disappeared.  This  much  having 
been  accomplished,  the  sulphate  of  strychnia  in  doses  of 
iro  to  53  of  a  grain  should  be  g-iven  before  each  meal.  At 
this  stag-e  the  interrupted  current  of  electricity,  used 
once  daily  for  ten  minutes,  will  do  g-ood.  While  there  is 
still  diplopia,  the  strychnia  and  electricity  would  do 
harm,  rather  than  g-ood. 

In  old  cases  of  ocular  paralysis,  when  there  can  be  no 
long-er  any  hope  of  restoration  of  power  to  the  paralyzed 
muscle,  surgery  will  do  good,  in  that  it  will  lessen  the 
field  of  diplopia  and  give  to  the  patient  a  more  natural 
pose  of  the  head.  The  operation  should  be  either  an 
extensive  shortening  or  advancement  of  the  paralyzed 
muscle,  and  never  even  a  partial  tenotomy  of  the  antag- 
onist. The  muscle  plane  should  be  changed  or  not, 
when  making  the  shortening  or  advancement,  as  may  be 
indicated  by  the  existence  or  non-existence  of  torsion. 


618  PARALYSIS   AND   PARESIS 

LAGOPHTHALMOS. 

The  condition  termed  "  lagophthalmos  "  was  so  named 
because  it  gave  to  the  human  eye  the  appearance  of  the 
eye  of  the  hare — always  open,  asleep  or  awake.  The 
cause  of  the  condition  is  disease  of  the  seventh  nerve  in 
its  course;  or  at  its  basal  or  cortical  centers,  or  between 
these  two — in  the  internal  capsule  or  in  the  corona 
striata.  In  either  case  there  is  a  greater  or  less  loss  of 
power  on  the  part  of  the  corresponding-  orbicularis,  and 
usually  the  muscles  of  the  face  are  also  involved.  The 
location  of  the  disease  or  injury  determines  the  array  of 
symptoms  to  be  presented  in  any  case. 

When  the  part  involved  is  the  basal  center  of  the  nerve, 
or  the  body  of  the  nerve  as  it  finds  its  way  out  to  be 
finally  distributed  to  all  the  muscles  of  the  face,  includ- 
ing1 the  orbicularis  of  the  corresponding"  side,  all  these 
muscles  will  be  paralyzed,  and  the  log^aphthalmos  will 
be  only  one  of  the  symptoms.  The  skin  of  the  forehead 
on  the  affected  side  is  smooth,  as  if  "ironed  out,"  and 
the  patient  is  wholly  unable  to  throw  it  into  wrinkles 
for  the  reason  that  this  half  of  the  anterior  part  of  the 
occipito-frontalis  is  supplied  by  the  diseased  nerve;  the 
corrug^ator  supercilii  must  also  be  inactive,  therefore 
the  brow  on  that  side  cannot  be  drawn  down;  the  vari- 
ous muscles  connected  with  the  nose  and  mouth,  action 
of  which  gx>es  so  far  to  give  agreeableness  of  expression  to 


OF    THE    OCULAR    MUSCLES.  619 

the  face,  cannot  receive  a  nerve  impulse,  therefore  they 
must  be  inactive,  and  the  face,  on  that  side,  becomes 
expressionless;  the  buccinator,  which  is  also  supplied  by 
the  seventh  nerve,  loses  its  power  and  thus  the  mastica- 
tion of  food  on  that  side  becomes  inconvenient — almost 
impossible — for  the  reason  that,  when  the  tongue 
presses  the  food  between  the  teeth,  the  buccinator  being 
unable  to  make  counter  pressure,  the  food  cannot  be 
kept  between  the  grinders.  Soon  the  patient  learns  to 
do  all  his  chewing  on  the  unaffected  side.  The  mouth 
is  always  drawn  toward  the  unaffected  side,  and  a 
laugh  will  be  confined  wholly  to  this  side.  The  patient 
drinks  with  difficulty  and  cannot  whistle.  All  of  these 
symptoms  will  be  associated  with  the  inability  to  close 
the  eye. 

Both  parts — the  voluntary  and  the  involuntary — of 
the  orbicularis  being  involved,  the  eye  will  be  wide  open, 
and  there  will  be  no  power  to  close  it.  Any  great  effort 
to  close  it  will  only  cause  the  eye  to  move  upward,  as  if 
to  hide  behind  the  upraised  lid.  The  lower  lid  will  not 
be  held  in  contact  with  the  globe,  hence  the  punctum 
will  be  displaced.  The  absence  of  the  batting  power 
makes  it  impossible  for  the  punctum  of  the  upper  lid  to 
carry  off  the  tears;  hence  there  must  be  an  excess  of 
tears  in  the  conjunctival  sac.  The  unprotected  eye 
becomes  irritable,  as  shown  by  conjunctival  redness,  ex- 


620  PARALYSIS   AND    PARESIS 

cessive  secretion  of  tears,  and  some  dread  of  light.  If 
the  eye  is  exposed  too  long  and  too  severely,  the  cornea 
may  ulcerate,  when  the  eye,  of  course,  becomes  painful. 
By  far  the  most  common  cause  of  lagophthalmos,  as- 
sociated with  the  other  symptoms  already  described,  is 
inflammation  of  the  middle  ear,  and  the  reason  is  not 
hard  to  find.  The  seventh  nerve,  as  it  passes  through 
the  aqueduct  of  Fallopius,  in  the  inner  bony  wall  of  the 
drum  cavity,  should  be  completely  covered  in  by  bone 
structure.  That  this  bone-covering  is  complete,  in 
many  cases,  is  made  evident  by  the  fact  that  otitis  media 
is  not  attended  by  involvement  of  the  seventh  nerve ; 
that  it  is  incomplete,  in  some  cases,  is  made  equally  evi- 
dent because  of  the  fact  that  in  some  cases  even  a  very 
slight  otitis  media  is  attended  by  paralysis  of  all  the 
muscles  of  the  face.  Whenever  there  is  a  break  in  the 
bony  covering,  the  mucous  membrane  lining  the  inner 
wall  of  the  drum  cavity  must  lie  directly  in  contact  with 
the  sheath  of  the  seventh  nerve,  hence  the  readiness 
with  which  an  inflammation  of  this  membrane  may  in- 
volve the  -nerve.  Catarrhal,  as  well  as  suppurative, 
inflammation  of  the  middle  ear,  in  such  cases,  almost 
always  causes  facial  paralysis.  When  such  is  the  cause 
of  facial  paralysis,  the  usual  symptoms  of  inflammation 
of  the  ear  are  present — namely:  pain,  fullness,  and  deaf- 
ness, with  some  fever.  The  objective  symptoms  are 


OF    THE   OCULAR    MUSCLES.  621 

also  present.  If  the  inflammation  causing-  the  paralysis 
is  between  the  basal  center  of  the  seventh  nerve  and  the 
point  where  the  eighth  nerve  parts  company  with  the 
facial  nerve,  to  find  its  terminals  in  the  internal  ear,  the 
resulting  pressure  will  cause  deafness,  as  well  as  pa- 
ralysis of  the  facial  muscles;  but  other  symptoms  and 
signs  of  otitis  media  will  be  absent.  In  the  latter  case 
the  paralysis  of  the  orbicularis  will  be  as  complete  as  in 
the  former.  If  the  inflammation  or  injury  of  the  facial 
nerve  is  at  some  point  between  where  it  leaves  the  aque- 
duct of  Pallopius  and  the  point  where  it  divides  into  its 
several  branches,  the  facial  paralysis  will  be  complete; 
but  the  hearing  will  not  be  involved,  nor  will  there  be 
any  other  symptoms  referable  to  the  ear.  In  all  of 
these  conditions  the  batting-  power  is  lost. 

When. the  cause  of  the  lag-ophthalmos  is  in  the  cortex, 
the  lids  are  not  so  widely  separated,  and  their  batting- 
power,  thoug-h  modified,  is  not  lost.  The  other  muscles 
of  the  face  may  not  be  involved.  If  the  disease  in  the 
cortex,  in  the  internal  capsule,  or  in  the  corona  radiata  is 
extensive,  other  symptoms  will  be  found  in  association 
with  the  lag-ophthalmos.  Such  cases  are  not  so  likely 
to  recover  full  voluntary  power  over  the  orbicularis. 

TREATMENT. 

Whatever  may  be  the  cause,  the  eye  should  be  pro- 
tected by  a  flap  until  such  time  as  the  lids  may  have 


622  PARALYSIS   AND    PARESIS. 

recovered  their  power;  otherwise,  the  cornea  may  ulcer- 
ate. If  otitis  media  is  the  cause,  this  condition  should 
be  so  treated  as  to  prevent  suppuration,  if  possible  ;  but 
if  suppuration  occurs,  the  disease  should  be  so  treated 
as  to  bring  it,  as  speedily  as  possible,  under  control. 
In  all  cases  the  iodide  of  potassium  and  the  bichloride  of 
mercury  should  be  administered  for  promoting-  absorp- 
tion of  inflammatory  deposits  within  the  sheath  of  the 
nerve.  In  this  work  these  drug's  can  be  greatly  aided 
by  the  fluid  extract  of  jaborandi,  in  twenty-drop  doses, 
three  times  a  day  for  the  first  two  weeks.  Strychnia 
should  be  given  only  when  a  return  of  voluntary  power 
to  the  facial  muscles  shows  that  the  pressure  of  inflam- 
matory deposits  has  been  relieved  more  or  less  com- 
pletely. When  the  cause  of  lagophthalmos  is  above  the 
basal,  or  reflex,  center,  sorbefacient  treatment  is  indi- 
cated; but,  as  already  stated,  recovery  is  both  slow  and 
doubtful  o 


CHAPTER  XII. 


MUSCLES  OF  THE  IRIS  AND  OF  THE 
CILIARY  BODY. 


THE  heading-  of  this  chapter  is  intended  to  convey  the 
idea  that  the  iris  has  more  than  one  muscle-,  and  that  in 
the  ciliary  body  there  is  more  than  one  muscle.  Both 
anatomy  and  physiology  g"ive  evidence  of  the  existence 
of  two  muscles  in  the  iris;  anatomy  shows  two  sets  of 
muscular  fibers  in  the  ciliary  body,  and  there  is  also 
physiologic  evidence  of  the  existence  of  two  independent 
muscles,  each  under  a  separate  innervation. 

MUSCLES  OF  THE  IRIS. 

At  one  time  in  the  history  of  medicine  it  was  taug-ht 
that  there  was  erectile  tissue  in  the  iris  which,  by  be- 
coming- filled  with  blood,  would  make  the  pupil  small, 
and,  by  ag-ain  becoming-  empty,  would  effect  the  dilatation 
of  the  pupil.  Other  theories  were  offered  from  time  to 
time,  accounting-  for  the  chang-eableness  of  the  pupil- 
lary opening-  in  the  iris,  without  taking-  into  account 
the  necessity  for  muscular  contraction  to  effect  these 

(623) 


624  MUSCLES   OF   THE   IRIS. 

changes.  As  early  as  the  tenth  century  an  Arabian 
physician  announced  his  belief  in  the  existence  of  mus- 
cles in  the  iris,  contractions  of  which  varied  the  size  of 
the  pupil,  his  only  evidence  being  physiologic.  In  his 
day  theie  were  no  means  of  investigation  to  determine 
anatomically  the  existence  of  muscle  structure  so  small. 
Descartes,  though  neither  an  anatomist  nor  a  physiolo- 
gist, announced  in  one  of  his  publications,  in  the  seven- 
teenth century,  that  muscles  in  the  iris  regulated  the 
pupillary  opening. 

The  existence  of  radiating  fibers  was  generally  con- 
ceded a  long  time  before  Berger  announced,  in  1701, 
that  orbicular  fibers  also  existed  in  the  iris.  It  was  not 
until  1812  that  the  microscope,  under  the  eye  of  Mau- 
noir,  revealed  the  existence  of  circular  fibers  in  the  iris 
of  the  bird.  Prom  that  time  to  the  present  there  has 
been  no  one  ready  to  deny  the  existence  of  the  circular 
muscle  of  the  iris.  The  microscope  has  since  demon- 
strated the  existence  of  the  sphincter  muscle  of  the  iris 
in  man.  It  is  known  to  be  a  circular  muscle-band,  about 
one  millimeter  wide,  at  the  pupillary  margin  of  the  iris 
and  nearer  its  posterior  surface. 

Radiating  muscular  fibers  in  the  iris  has  been  a  mat- 
ter of  much  discussion,  but  now  the  preponderance  of 
evidence  is  in  favor  of  the  existence  of  such  fibers. 
Grunhagen,  Collins,  and  others  have  taught  that  there  is 


MUSCLES   OF    THE    IRIS.  625 

elastic  tissue  in  the  iris  that  effects  the  dilatation  of  the 
pupil  whenever  action  of  the  sphincter  is  inhibited — that 
the  dilatation  is  effected  passively,  and  not  actively. 
Juler,  at  the  eighth  International  Congress  of  Ophthal- 
mology, in  1894,  announced  that,  by  a  new  method  of 
investigation,  he  had  been  able  to  show,  under  the 
microscope,  the  radiating  muscular  structure  of  the  iris. 
This  anatomic  evidence,  associated  with  the  evidence 
given  by  physiology,  removes  the  question  of  the  exist- 
ence of  a  pupil-dilator  muscle  entirely  from  the  domain 
of  doubt.  Juler  has  demonstrated  that  the  radiating 
muscular  fibers  have  their  origin  at  the  attached  margin 
of  the  iris,  and  pass  to  the  pupillary  margin,  where  they 
become  blended  with  the  sphincter  muscle. 

Petit  observed,  in  1727,  that  a  division  of  the  cervical 
sympathetic  caused  contraction  of  the  pupil;  and  Biffi, 
in  1846,  showed  that  stimulation  of  the  cervical  sympa- 
thetic effected  dilatation  of  the  pupil.  By  a  similar 
method  of  investigation,  Mayo,  in  1823,  proved  that  the 
sphincter  muscle  of  the  iris  is  supplied  by  the  third 
cranial  nerve,  a  division  of  which  dilates  the  pupil, 
while  stimulation  of  this  nerve  makes  the  pupil  contract. 

There  is  no  room  for  doubting  the  existence  of  these 
two  muscles  in  the  iris  ;  and  that  they  are  antagonistic— 
the  one  contracting  the  pupil,  the  other  effecting  its  dila- 
tation— is  as  little  open  to  doubt. 


626  MUSCLES   OF    THE    IRIS. 

Those  fibers  of  the  third  nerve  and  of  the  cervical 
sympathetic,  that  give  power,  respectively,  to  the  pupil- 
contractor  muscle  and  the  pupil-dilator  muscle,  pass 
first  to  the  ciliary  ganglion,  in  which  they  are  joined  by 
fibers  from  the  fifth  nerve.  From  this  g-anglion  the 
several  short  ciliary  nerves,  each  containing  fibers  from 
the  three  different  sources,  make  their  way  to  the  pos- 
terior part  of  the  eye,  which  they  enter.  They  are 
finally  distributed  to  the  ciliary  body  and  the  iris,  giv- 
ing sensation  to  these  structures  and  power  to  their  mus- 
cular parts. 

The  function  of  the  iris  is  to  regulate  the  quantity  of 
light  that  enters  the  eye,  and  this  it  does  reflexly.  A 
too-bright  light  makes  it  necessary  for  the  pupil  to  be 
made  smaller,  which  is  effected  by  an  impulse  sent  from 
the  nucleolus  of  the  third  nerve-center  that  controls  the 
sphincter  of  the  iris;  a  dim  light  takes  the  nucleolus  of 
the  sphincter  off  its  guard  and  allows  the  influence  of 
the  cervical  sympathetic  on  the  radiating  fibers  of  the 
iris  to  effect  the  dilatation  of  the  pupil.  There  should  be 
harmony  in  the  antagonism  of  these  two  muscles,  for 
the  purpose  of  properly  regulating  the  quantity  of  the 
light  that  enters  the  eye.  The  iris  also  serves  to  cut  off 
the  peripheral  rays  of  every  cone  of  light,  which  enables 
the  refractive  media  to  make  a  focus  sharper  than  it 
would  be  if  spherical  aberration  were  not  thus  prevented. 


MUSCLES   OP    THE   IRIS.  627 

In  most  cases  the  muscles  of  the  iris  do  their  work 
well.  There  are  cases,  however,  in  which  either  the 
sphincter  muscle  is  too  weak,  because  of  poor  develop- 
ment or  slight  innervation,  or  the  pupil-dilator  muscle 
is  abnormally  strong  from  hyper-development  or  over- 
stimulation;  as  a  result,  the  pupil  is  too  large  under 
ordinary  light  and  when  shaded.  Under  the  stimulus 
of  strong  light  it  contracts;  but  if  such  exposure  is  pro- 
longed, the  contraction  of  the  sphincter  becomes  painful. 
Any  one  of  several  symptoms  of  eye-strain  may  be 
caused  by  prolonged  contraction  of  a  weak  sphincter  of 
the  iris.  Such  patients  cannot  endure,  with  any  com- 
fort, prolonged  exposure  to  bright  light,  whether  nat- 
ural or  artificial.  The  author  has  observed  a  fairly 
large  number  of  such  cases,  and  has  had  a  fair  degree  of 
success  in  managing  them.  A  weak  pupil-dilator  mus- 
cle is  not  likely  to  be  the  source  of  annoying  symptoms. 
A  patient  with  weak  pupil  contractors  should  have  these 
muscles  treated,  regardless  of  what  else  must  be  done 
for  the  relief  of  other  conditions  that  may  cause  strain. 

TREATMENT. 

Patients  with  large  pupils,  who  suffer  when  exposed 
to  bright  light,  may  have  their  pupil  contractors  devel- 
oped and  strengthened  by  exercise.  The  method  is  as 
follows :  Before  retiring  at  night,  the  patient  should 


628  MUSCLES   OF    THE   CILIARY   BODY. 

sit  before  a  fairly  bright  lamp,  holding-  in  one  hand  a 
densely  opaque  cardboard  which  she  should  place  be- 
tween her  and  the  light  at  regular  intervals  of  two  or  three 
seconds,  looking  all  the  time  in  the  direction  of  the  light. 
Thus  there  would  be  alternate  exposure  of  the  eyes  to 
light  and  darkness,  producing  rhythmic  contraction  and 
relaxation  of  the  sphincter  ol  the  iris.  For  this  exercise 
ten  minutes  will  be  sufficient;  but  should  the  e}Tes  be- 
come fatigued,  the  exercise  should  cease  sooner.  The 
exercise  should  be  repeated  every  night  for  a  long  wrhile. 
In  the  absence  of  the  exercise  treatment,  the  only 
thing  to  be  advised  is  the  wearing  of  smoke  lenses  con- 
stantly, or  whenever  the  eyes  are  to  be  exposed  to  bright 
light.  These  lenses  allow  the  pupils  to  become  more  or 
less  enlarged,  which  means  that  the  sphincters  are 
thereby  rested.  This  method  favors  the  muscle  in  its 
weakness,  and  is  not  to  be  preferred  to  the  exercise 
treatment,  for  the  latter  means  that  the  sphincter  will 
be  made  strong  eventually. 

MUSCLES  OF  THE  CILIARY  BODY. 

It  was  not  known  until  1846  that  there  were  any  mus- 
cular fibers  in  the  ciliary  body;  but  at  this  time  Bowman 
discovered,  with  the  microscope,  muscular  fibers  which 
were  parallel  with  the  meridians  of  the  eye,  hence  prop- 
erly called  them  "meridional."  These  he  considered  as 


MUSCLES   OF    THE    CILIARY    BODY.  629 

having"  their  origin  in  the  anterior  part  of  the  ciliary 
body  and  their  insertion  in  the  anterior  part  of  the 
choroid.  He  named  this  newly  discovered  muscle  the 
"tensor  of  the  choroid,"  and  in  it  he  thought  he  had 
found  the  secret  of  the  power  of  accommodation.  His 
explanation  was  that  this  muscle,  by  making  tense  the 
choroid,  so  compressed  and  changed  the  shape  of  the 
vitreous  as  to  force  the  lens  forward,  thereby  increasing 
the  distance  between  the  macula  and  the  lens  sufficiently, 
he  thought,  to  account  for  the  phenomena  of  accommo- 
dation. Before  that  time  no  theory  of  accommodation 
had  included  the  idea  that  there  existed,  in  the  ciliary 
body,  a  muscle.  So  thoroughly  satisfied  was  Bowman 
that  he  did  not  pursue  his  investigations  further,  else  he 
would  have  discovered,  also,  the  circular  fibers  which 
were  discovered  later  by  H.  Miiller.  Long  before  the 
discovery  of  either  Bowman's  muscle  or  Miiller's  muscle 
(that  there  are  two  muscles  will  be  shown  farther  on), 
Young  had  demonstrated  an  increase  in  the  curvature  of 
the  crystalline  lens  in  the  act  of  accommodation.  Miil- 
ler thought  that,  by  contraction  of  the  circular  muscle 
discovered  by  himself,  direct  pressure,  by  the  ciliary 
processes,  on  the  periphery  of  the  lens,  caused  the  in- 
crease in  convexity;  but  Helmholtz  had  taught  that  the 
increase  in  curvature  was  due  to  inherent  elasticity  of 
the  lens,  which  was  allowed  to  manifest  itself  because  of 


630  MUSCLES   OF    THE   CILIARY    BODY. 

relaxation  of  the  zonula,  effected  by  the  contraction  of 
Bowman's  muscle. 

It  would  seem  that  all  authors  are  agreed  that  in  the 
ciliary  body  there  are  two  sets  of  muscular  fibers — one 
set  running-  parallel  with  the  meridians,  and  another  col- 
lection of  fibers  forming  a  circle  in  the  anterior  part  of 
the  ciliary  body.  There  is  universal  agreement,  also, 
that  one  or  the  other  of  these  muscles,  or  both,  is  the 
active  agent  in  accommodation.  It  is  also  universally 
conceded  that  the  accommodative  muscle  is  supplied  by 
the  third  nerve. 

The  microscope  has  revealed  the  fact  that  there  are 
two  muscles — or,  at  least,  two  different  arrangements  of 
muscular  fibers — in  the  ciliary  body;  the  existence  of  two 
independent  muscles,  each  getting  its  nerve  supply  from 
a  separate  source,  appears  to  be  shown  by  physiology. 
Young,  in  1801,  demonstrated  increased  curvature  of  the 
lens  in  accommodation;  Helmholtz  accounted  for  this  in 
relaxation  of  the  zonula  by  a  contraction  of  the  muscle 
of  Bowman — the  so-called  "tensor  of  the  choroid  "  —when 
he  could  have  accounted  for  it  more  easily  in  a  contrac- 
tion of  the  muscle  of  Miiller,  which,  by  making  more 
narrow  the  zone  between  the  ciliary  processes  and  the 
periphery  of  the  lens,  necessarily  relaxed  the  suspensory 
ligament  of  the  lens,  thus  allowing  the  lens  to  manifest 
its  elasticity.  By  becoming'  more  convex,  the  lens  would 


MUSCLES   OF    THE    CILIARY    BODY.  631 

necessarily  take  up  the  laxness  of  the  ligament.  A  fact 
strongly  favoring  the  idea  that  the  muscle  of  accommo- 
dation is  Miiller's  muscle  is  that  Coccius  has  seen,  in 
eyes  on  which  an  iridectomy  had  been  done,  a  narrowing 
of  the  circumlental  zone  in  the  act  of  accommodation. 
It  is  easier  to  understand  how  the  circular  muscle 
(Miiller's)  could  relax  the  zonula,  and  thus  enable  the 
lens  to  become  more  convex,  than  it  is  to  understand  how 
Bowman's  muscle  could  effect  the  same  changes.  In 
fact,  it  would  appear  that,  if  Bowman's  muscle  is  the 
active  agent  in  accommodation,  the  zonula  would  be 
made  more  tense,  and  would,  therefore,  prevent  the  lens 
from  increasing  in  convexity;  but,  on  the  contrary,  the 
lens  would  be  compressed  toward  its  periphery.  If 
Bowman's  muscle  is  the  active  agent  in  accommodation, 
it  is  supplied  by  the  third,  or  mortor  oculi,  nerve,  and  the 
change  of  the  lens  would  be  more  in  position  than  in 
curvature;  the  change  in  curvature  would  not  be  an  in- 
crease in  spherical  curvature,  but  it  would  be  the  forma- 
tion of  a  lenticonus.  There,  then,  could  be  no  possible 
use  for  the  circular  muscle  of  Miiller.  If  the  Miiller 
muscle  is  the  active  agent  in  accommodation,  it  is  sup- 
plied by  the  third,  or  mortor  oculi,  nerve,  and  the  change 
in  the  lens  would  not  be  in  position,  but  wholly  in  curva- 
ture; the  change  in  curvature  would  be  in  an  increase 
of  the  sphericity  of  the  lens — a  shortening  of  the  radius 


632  MUSCLES   OF    THE    CILIARY   BODY. 

of  the  anterior  curve — made  possible  by  a  narrowing  of 
the  circumlental  zone.  If  this  is  the  work  of  the  Miiller 
muscle,  there  would  still  remain  a  work  to  be  done  by  the 
Bowman  muscle,  which  will  be  set  forth  farther  on. 

The  answer  to  the  question,  "Is  the  muscle  of  Bow- 
man or  the  muscle  of  Muller  the  active  agent  in  accom- 
modation ?  "  must  come  from  a  study  of  the  actual  change 
that  occurs  in  the  lens  in  the  accommodative  act.  If 
Bowman's  muscle  is  the  muscle  of  accommodation, 
Tscherning's  views  as  to  the  condition  of  the  zonula  and 
the  state  of  the  lens  in  accommodation  must  be  correct — 
that  is,  the  zonula  must  be  on  the  stretch,  and  the  ante- 
rior surface  of  the  lens  must  assume  the  shape  to  which 
he  has  given  the  name  "lenticonus."  If  in  accommoda- 
tion the  zonula  is  relaxed,  a  more  rapid  spherical  curva- 
ture of  the  lens  is  possible,  and  these  changes  can  be  ef- 
fected only  by  the  contraction  of  Miiller's  muscle.  Helm- 
holtz  would  be  correct,  at  least  in  part;  he  would  be 
wrong  only  in  the  thought  that  the  narrowing  of  the 
circumlental  zone  had  been  effected  by  Bowman's  muscle. 

Is  the  change  in  the  lens  the  formation  of  a  lenticonus, 
according  to  Tscherning,  or  is  it  an  increase  in  the 
curvature  of  the  anterior  surface,  according  to  Young, 
Helmholtz,  Bonders,  and  many  others?  One  thing  should 
be  conceded  at  the  outset — that  is,  there  is  in  accommo- 
dation a  narrowing  of  the  circumlental  zone,  the  space 


MUSCLES    OF    THE    CILIARY    BODY.  633 

between  the  ciliary  processes  and  the  periphery  or  equa- 
tor of  the  lens.  All  writers  agree  that  in  the  absence 
of  accommodation  the  two  surfaces  of  the  lens  are  spher- 
ical. Now,  suppose  the  eye  of  one  individual  to  be  em- 
metropic,  and  the  eye  of  another  person  to  be  hyperopic. 
The  emmetropic  eye,  without  any  accommodative  effort, 
has  vision  equal  ^x,  and  that  through  a  lens  whose  sur- 
face must  be  conceded  to  be  spherical.  The  person  with 
the  hyperopic  eye  (say  of  3.  D),  by  the  aid  of  his  accom- 
modative power,  also  has  vision  equal  ||.  Surfaces  dif- 
ferently curved  cannot  refract  light  in  the  same  way. 
If  the  emmetropic  eye  saw  through  a  lens  having  a 
spherically  curved  surface,  the  hyperopic  eye,  in  the 
act  of  accommodation  for  distant  seeing,  must  have  had 
also  a  lens  whose  surface  was  spherically  curved.  If  ac- 
commodation of  3.  D  for  distant  seeing  does  not  produce 
a  lenticonus,  is  it  possible  that  accommodation  of  3.  D  for 
near  seeing  will  do  so?  Again,  suppose  one  person  to  be 
emmetropic  and  sixty  years  old,  but  still  possessing  a 
perfectly  transparent  lens;  and  suppose  another  person 
emmetropic  and  sixteen  years  old.  These  two  persons 
will  have  equally  good  distant  vision,  without  any  accom- 
modative effort  on  the  part  of  either.  At  a  distance  of 
thirteen  inches  the  older  person,  not  having  any  accom- 
modative power,  cannot  see  to  read;  while  the  younger 
person,  by  the  exercise  of  accommodation,  sees  every 


634  MUSCLES   OP    THE    CILIARY   BODY. 

word  and  letter  perfectly.  On  placing1  a  plus  3.  D  lens 
before  the  eye  of  the  older  person,  everything1  on  the 
page  becomes  as  clear  and  as  distinct  to  him  as  it  is  to 
the  young-er  person.  The  lens  of  the  older  person  has 
not  lost  its  sphericity  in  changing*  the  point  of  view  from 
twenty  feet  to  thirteen  inches,  for  he  has  no  accommoda- 
tive power;  but  for  him  the  plus  3.  D  spherical  lens  has 
made  divergent  rays  parallel,  and  these  parallel  rays  are 
easily  and  accurately  focused  on  his  retina  by  his  own 
spherically  curved  crystalline  lens.  If  the  two  spher- 
ically curved  bodies — the  presbyopic  lens  and  his  crys- 
talline lens — have  made  the  old  man  see  perfectly,  has  it 
been  necessary  for  the  surface  of  the  crystalline  lens  in 
the  young1  person  to  become  changed  to  a  lenticonus  in 
order  that  he  might  see  distinctly  at  thirteen  inches? 
Either  the  surface  of  the  crystalline  lens  in  the  young 
person  has  not  changed  from  a  spherical  curve,  when 
there  was  no  accommodation,  to  a  lenticonus,  in  accom- 
modation, or  a  presbyopic  lens  should  be  a  lenticonus,  and 
not  spherical.  In  conclusion,  this  statement  will  be 
made  without  fear  of  contradiction:  Spherical  refractive 
surfaces,  with  the  peripheral  rays  cut  off  by  a  perfo- 
rated diaphragm,  can  reproduce  perfectly,  point  for 
point,  an  image  of  the  object  from  which  the  rays  of 
light  have  come. 

For  the  reasons  given  above,  the  logical  conclusion  is 


MUSCLES   OF    THE    CILIARY   BODY.  635 

that  in  accommodation  the  zonula  is  relaxed  by  a  nar- 
rowing- of  the  circumlental  zone,  that  this  laxness  is 
taken  up  by  an  increase  in  the  convexity  of  the  elastic 
crystalline  lens,  and  that  these  changes  can  be  effected 
only  by  a  contraction  of  Miiller's  muscle.  Since  Miil- 
ler's  muscle  is  the  active  agent  in  accommodation,  it  is 
supplied  by  the  third  nerve. 

Since  Tscherning  published  his  views  concerning-  ac- 
commodation, it  has  been  demonstrated  by  Hess  that  the 
zonula  is  relaxed  in  accommodation;  and  Priestly  Smith 
has  claimed  that  it  is  possible  for  the  anterior  surface  of 
the  lens  to  assume  the  lenticonus  shape,  in  accommoda- 
tion, when  the  zonula  is  relaxed. 

As  already  stated,  there  is  a  use  for  the  muscle  of 
Bowman,  reg-ardless  of  the  fact  that  it  is  not  the  active 
agent  in  accommodation.  There  is  a  reason  for  believ- 
ing- that  this  muscle,  like  the  radiating-  muscle  of  the 
iris,  is  supplied  by  the  cervical  sympathetic,  through  the 
medium  of  the  ciliary  ganglion.  It  is  generally  taught 
that  at  least  some  of  the  meridional  fibers  extend  from 
the  anterior  part  of  the  choroid  through  the  ciliary  bod}*, 
terminating  in  the  part  occupied  by  the  circular  muscle 
(Miiller's)  in  the  region  of  the  attachment  of  the  zonula 
to  the  ciliary  processes.  They  pursue  such  a  course  and 
are  so  related  to  the  suspensory  ligament  that  it  appears 
highly  probable  that  it  is  through  the  active  agency  of 


636  MUSCLES   OF    THE   CILIARY   BODY. 

these  fibers  (Bowman's  muscle)  that  the  crystalline  lens 
is  made  to  assume  a  mathematically  correct  position  in 
its  bed  in  the  anterior  part  of  the  vitreous.  This  normal 
and  mathematically  correct  position — the  position  that  it 
must  occupy  when  there  is  no  corneal  astigmatism — is 
such  that  the  antero-posterior  axis  shall  coincide  with 
the  visual  axis,  and  that  its  equatorial  plane  shall  be 
parallel  with  the  equator  of  the  eye.  In  the  process  of 
development  the  lens,  in  many  instances,  may  passively 
assume  the  proper  position;  and,  if  so,  there  would  be 
nothing"  for  Bowman's  muscle  to  do;  but  in  many  in- 
stances the  passive  position  assumed  by  this  lens  in  its 
development  would  not  be  mathematically  correct,  hence 
the  need  of  some  active  agent  for  readjusting.  This 
agent  could  be,  and  doubtless  is,  Bowman's  muscle,  and 
the  medium  through  which  this  muscle  could  effect  the 
readjustment  is  the  suspensory  ligament  —  the  zonula. 
The  agent  calling  on  Bowman's  muscle  to  do  this  work 
would  be  the  guiding  sensation  of  the  retina,  which  is 
the  taskmaster  of  all  the  ocular  muscles,  intrinsic  and 
extrinsic.  The  time  for  effecting  this  readjustment 
would  be  after  birth,  for  before  birth  the  guiding  sensa- 
tion must  be  dormant.  The  task  of  readjustment  is, 
doubtless,  fully  accomplished  in  infancy,  or,  at  the  latest, 
early  in  childhood.  It  is  not  more  wonderful  that  Bow- 
man's muscle  should  be  endowed  with  this  unvolitional 


MUSCLES   OF    THE    CILIARY    BODY.  637 

power  than  it  is  that  Muller's  muscle,  likewise  under 
the  control  of  the  guiding  sensation,  should  be  endowed 
with  power  to  mathematically  adjust  vision  for  all  dis- 
tances. 

If  Bowman's  muscle  can  readjust  the  lens  in  an  eye 
whose  cornea  is  free  from  astigmatism,  so  that  its  posi- 
tion shall  be  mathematically  correct,  is  it  not  also  pos- 
sible that  the  same  muscle  may  be  the  active  agent  in 
producing  a  lenticular  astigmatism  at  right  angles  to  a 
corneal  astigmatism  for  the  purpose  of  neutralizing  it? 
Suppose  a  case  of  corneal  astigmatism  of  2.  D,  with  the 
meridian  of  greatest  curvature  at  one  hundred  and  eighty 
degrees;  to  correct  this  by  a  neutralizing  lenticular  astig- 
matism, an  impulse  would  have  to  be  sent  to  a  collection 
of  meridional  fibers,  either  directly  above  or  below  the 
lens,  a  contraction  of  which  would  tilt  the  lens  on  its  hori- 
zontal axis  so  as  to  increase  the  refractive  power  of  its 
vertical  meridian  to  the  extent  of  2.  D.  Thus  would  the 
corneal  astigmatism  be  neutralized.  It  is  well  known 
that  the  tilting  of  a  lens  increases  its  refractive  power  at 
right  angles  to  the  axis  of  tilting.  Tilting  a  lens  forty- 
five  degrees  practically  doubles  its  strength  at  right  an- 
gles to  the  axis  of  rotation,  without  changing  its  power 
in  line  with  this  axis;  and  in  this  way  a  spherical  lens  is 
made  to  have  an  astigmatic  effect.  The  strength  of  the 
crystalline  lens  is  so  great  that  a  very  slight  tilting 


638  MUSCLES   OF    THE    CILIARY   BODY. 

would  produce  a  considerable  astigmatic  effect.  L/entic- 
ular  astigmatism  cannot  be  effected  by  a  contraction  of 
Miiller's  muscle,  but  it  can  be  easily  effected  by  the  ac- 
tion of  individual  fibers  cf  Bowman's  muscle.  How  the 
guiding  sensation  can  select  and  call  into  action  a  few 
fibers  of  Bowman's  muscle,  yet  allow  all  the  balance 
of  this  muscle  to  remain  quiet,  is  not  subject  to  expla- 
nation. 

The  author  does  not  have  to  suppose  a  case  of  corneal 
astigmatism  that,  in  some  way  or  other,  was  neutralized 
automatically,  to  a  considerable  extent,  for  many  years. 
His  own  corneal  astigmatism  is  2.50  D,  and  has  been  so 
since  1889,  when  Swan  M.  Burnett,  of  Washington,  meas- 
ured it  with  Javal's  ophthalmometer.  The  first  attempt 
at  astigmatic  correction  by  artificial  means  was  made  in 
1882,  under  the  influence  of  atropine.  The  correcting 
cylinder  for  each  eye  was  plus  .65.  In  1885,  again  under 
a  mydriatic,  L.  Webster  Fox,  of  Philadelphia,  found  the 
correcting  cylinder  for  each  eye  to  be  plus  .75.  In  1887 
a  plus  1.  cylinder  for  each  eye  was  given.  Again,  in 
1888,  a  plus  1.25  cylinder  for  each  eye  fully  corrected  the 
manifest  astigmatism,  a  mydriatic  again  being  used — this 
time,  homatropine,  gr.  viii.  to  water  oz.  i.  Ten  drops, 
one  every  five  minutes,  were  placed  in  each  eye,  and 
at  the  end  of  half  an  hour  the  examination  was  made. 
From  that  time  until  1895  more  astigmatism  became 


MUSCLES   OF    THE    CILIARY    BODY.  639 

manifest,  but  the  stronger  cylinder  was  not  given  until 
that  date.  The  cylinder  then  given  was  plus  2.  D  for 
each  eye.  In  1900  the  cylinder  given  for  the  right  eye 
was  plus  2.25,  and  that  given  the  left  eye  was  plus  2.50 — 
practically  a  full  correction  of  the  corneal  astigmatism, 
which  during  at  least  eleven  years  had  remained  the 
same,  as  shown  by  the  Javal  ophthalmometer. 

The  author  has  thus  related  his  own  experience  for  the 
purpose  of  giving  emphasis  to  two  points:  (1)  There  was 
a  lenticular  astigmatism  that  almost  completely  neutral- 
ized the  corneal  astigmatism  up  to  the  age  of  twenty- 
eight  years;  (2)  the  power  that  effected  the  neutralizing 
lenticular  astigmatism  was  not  suspended  by  the  repeated 
use  of  mvdriatics,  and  this  power,  therefore,  could  not 
have  been  given  through  the  fibers  of  the  third  nerve 
that  come  from  the  ciliary  ganglion.  The  logical  con- 
clusion is  that  the  lenticular  astigmatism  was  produced 
by  fibers  of  Bowman's  muscle,  and  that  these  fibers  de- 
rived their  power  from  the  cervical  sympathetic. 

A  personal  experience,  similar  to  that  through  which 
the  author  has  passed,  has  been  related  by  Edward  Jack- 
son, of  Denver.  What  Jackson's  explanation  is,  the  au- 
thor does  not  know.  Doubtless  many  others  have  had 
a  similar  personal  experience;  and  it  is  not  too  much  to 
say  that  every  observer  has  had  such  cases  in  his  prac- 
tice. Occasionally  men  of  large  experience  have  seen 


640  MUSCLES   OF    THE   CILIARY    BODY. 

cases  of  astigmatism  to  be  accounted  for  only  by  an  as- 
tigmatic condition  of  the  crystalline  lens. 

It  may  be  that,  in  some  cases,  a  much  higher  degree 
than  2.50  D  of  corneal  astigmatism  could  be  neutralized 
by  a  lenticular  astigmatism.  It  is  true,  nevertheless, 
that,  in  many  cases,  even  a  low  degree  of  astigmatism  is 
not  always  thus  neutralized,  the  Bowman  muscle  being 
unable,  from  some  cause,  to  effect  the  necessary  change 
in  the  lens. 

If  a  tilting  of  the  lens  by  contraction  of  a  single  part 
of  Bowman's  muscle  is  not  the  cause  of  the  lenticular 
astigmatism,  the  simultaneous  and  equal  action  of  two 
opposite  parts  of  Bowman's  muscle,  by  making  tense  the 
corresponding  parts  of  the  zonula,  could  so  compress  the 
part  of  the  lens  intervening  as  to  increase  its  refractive 
power,  thus  effecting  lenticular  astigmatism.  It  would 
appear  that,  in  one  of  these  two  ways,  the  muscle  of 
Bowman  causes  a  neutralizing  lenticular  astigmatism. 
If  this  change  is  caused  by  a  tilting  of  the  lens,  it  is 
reasonable  to  suppose  that  the  work  of  tilting  could  be 
transferred  from  one  part  of  the  muscle  to  another  part 
directly  opposite.  For  instance,  in  the  production  of  a 
lenticular  astigmatism  for  neutralizing  a  corneal  astig- 
matism— meridian  of  greatest  curvature,  vertical — the 
lens  could  be  tilted  on  its  vertical  axis  by  contraction  of 
either  the  nasal  or  the  temporal  part  of  Bowman's  mus- 


MUSCLES    OF    THE    CILIARY   BODY.  641 

cle;  for  the  effect  would  be  the  same,  whether  the  nasal 
part  of  the  lens  is  thrown  forward  by  contraction  of  the 
temporal  part  of  the  muscle,  or  thrown  backward  by  a 
contraction  of  the  nasal  part  of  the  muscle.  Both  of 
these  parts  would  have  to  contract  simultaneously  and 
equally  if  the  lenticular  astigmatism  is  a  result  of  change 
in  curvature,  and  not  a  change  in  position.  In  either  in- 
stance, the  work  done  would  be  strain,  and  possibly  one 
of  the  worst  forms  of  eye-strain. 

After  the  foregoing  study  of  the  muscles  located  in 
the  ciliary  body,  this  chapter  may  be  concluded  with  a 
study  of  the  normal  work  required  of  each  in  some  con- 
ditions of  refraction,  and  the  abnormal  work  required  of 
them  in  other  states  of  refraction. 

THE  FUNCTION  OF  THE  MULLER  MUSCLE. — No  mus- 
cle of  the  eye  is  ever  called  on  to  do  either  normal  or  ab- 
normal work  for  any  other  purpose  than  the  improve- 
ment of  vision,  and  these  calls  are  always  made  b}r  the 
guiding  sensation,  which  resides  in  the  macula,  or,  at 
the  farthest,  within  the  retinal  area  of  binocular  fusion. 
The  contraction  of  Miiller's  muscle  is  intended  only  to 
increase  the  refractive  power  of  the  crystalline  lens 
equally  in  all  of  its  meridians.  This  change  in  the  re- 
fractive power  of  the  lens  is  effected  by  two  agents, 
Miiller's  muscle  being  the  active  agent  and  the  elasticity 
of  the  lens  being  the  passive  agent.  When  the  Miiller 


642  MUSCLES  OF    THE   CILIARY    BODY. 

muscle  is  at  rest,  the  zonula  is  tense,  and,  by  its  pressure 
against  the  lens,  suspends  the  elasticity  of  the  latter,  in 
which  state  it  has  its  minimum  power  of  refraction. 
When  the  guiding  sensation  calls  for  a  sharper  image 
on  the  macula,  the  response  comes  in  an  impulse  sent 
through  those  fibers  of  the  third  nerve  that  end  in  the 
muscle  of  accommodation  (Miiller's).  At  once  this 
muscle  contracts  equally  in  its  entire  extent,  relaxing 
the  zonula,  the  laxness  of  which  is  at  once  taken  up  by 
an  increase  in  the  convexity  of  the  lens  by  its  own  elas- 
ticity. The  degree  of  contraction  of  the  muscle  is  reg- 
ulated with  mathematical  precision,  and  the  change  in 
refractive  power  of  the  lens  is  only  enough  to  satisfy 
the  guiding  sensation. 

EMMETROPIA. — In  this  condition  of  refraction,  Miil- 
ler's muscle  is  never  called  into  action  when  the  object 
looked  at  is  in  the  distance;  but  when  the  point  of  fixa- 
tion is  at  thirteen  inches,  in  response  to  a  demand  from 
the  guiding  sensation,  an  impulse  is  sent  to  this  muscle 
sufficiently  powerful  to  effect  a  contraction  that  will  in- 
crease the  refraction  of  the  crystalline  lens  by  3.  D.  At 
nine  inches  a  4.  D  impulse  must  be  sent  to  the  muscle; 
but  when  the  point  of  fixation  is  at  the  distance  of 
1  M,  only  a  1.  D  impulse  is  needed.  Looking  again  into 
practical  infinity — any  distance  beyond  twenty  feet — the 
Miiller  muscle  goes  into  a  state  of  rest,  to  be  aroused 


MUSCLES   OF    THE   CILIARY    BODY.  643 

into  activity  again  only  when  the  point  of  view  is  near 
by.  In  distant  seeing1,  not  only  is  the  muscle  of  accom- 
modation at  rest,  but  all  of  the  recti;  and  the  obliques 
should  also  be  in  a  state  of  rest,  and  they  will  be  in  this 
state  if  there  is  orthophoria.  As  shown  elsewhere,  the 
brain-center  controlling-  the  ciliary  muscle  (Miiller's)  is 
in  some  way  associated  with  the  third  conjugate  center 
( convergence  center),  so  that  for  every  dioptre  of  ac- 
commodation there  is  a  convergence  of  each  visual  axis 
of  nearly  two  degrees  of  arc,  which  would  mean  about 
four  degrees  of  prism — a  point  not  made  clear  in  the 
study  of  pseudo-esophoria. 

In  emmetropia  and  orthophoria  everything  is  favorable 
for  comfort  in  the  use  of  the  eyes.  Such  eyes,  under  or- 
dinary use,  can  give  trouble  only  when  in  the  emme- 
tropic  eye  there  is  a  weak  muscle  of  accommodation  or 
when  the  orthophoria  is  asthenic.  What  should  be  done 
for  the  asthenic  orthophoria  has  already  been  set  forth; 
what  should  be  done  to  strengthen  a  weak  muscle  of  ac- 
commodation will  be  shown  farther  on  in  this  chapter. 

In  a  normal  condition,  the  strength  of  Miiller's  muscle 
varies  with  the  age  of  the  patient,  until  advancing  years 
deprive  it  of  all  power.  The  table  showing  the  varia- 
tion in  strength,  as  given  by  Jackson,  is  probably  as 
nearly  correct  as  any.  The  error,  if  any,  is  in  the  show- 
ing of  too  much  ciliary  power  after  the  age  of  thirty 


644  MUSCLES   OF    THE   CILIARY   BODY. 

years.  This  table  shows  the  relative  or  associated  ac- 
commodation, and  is  much  greater  than  would  be  shown 
if  accommodation,  unassociated  with  convergence,  were 
tested  with  concave  lenses.  Jackson's  table  is  as  fol- 
lows: 


Accommodation 

Distance  of  Point 

Age. 

in  Dioptres. 

of  Fixation  —  Inches. 

10 

14. 

2.81 

15 

12. 

3.28 

20 

10. 

8.94 

25 

9. 

4.4 

30 

8. 

4.9 

35 

7. 

5.6 

40 

5.5 

7.1 

45 

4. 

9.84 

50 

2.5 

15.75 

55 

1.25 

31.5 

60 

.5 

75.74 

65 

.0 

.00 

The  above  table  shows  that  the  amplitude  of  accom- 
modation, which  is  the  distance  between  the  far  and  the 
near  points,  grows  less  with  advancing  years,  until,  at 
the  age  of  sixty-five  years,  the  near  point  has  receded 
so  far  that  it  becomes  one  with  the  far  point. 

The  recession  of  the  near  point  is  due  either  to  an  ac- 
tual weakening  of  Miiller's  muscle  or  to  a  gradual  loss  of 
elasticity  of  the  lens,  probably  both.  If  the  muscle  could 
be  kept  strong,  the  elasticity  of  the  lens  would  doubtless 


MUSCLES   OF    THE   CILIARY    BODY.  645 

be  maintained  longer.  The  method  for  keeping  the  cil- 
iary muscle  strong  will  be  set  forth  in  answer  to  the 
question:  ' '  Can  presbyopia  be  deferred  ?  ' ' 

HYPEROPIA  AND  HYPEROPIC  ASTIGMATISM. — In  ei- 
ther of  these  conditions  of  refraction  the  guiding  sensa- 
tion will  call  for  activity  of  Miiller's  muscle  in  both  dis- 
tant and  near  seeing.  In  hyperopia  the  accommodation, 
unassociated  with  convergence,  must  effect  just  such 
an  increase  of  the  refractive  power  of  the  lens,  for  dis- 
tant vision,  as  will  render  sharp  the  image  of  the  object 
of  fixation.  This  necessity  for  the  exercise  of  the  ac- 
commodation for  distant  seeing  disturbs  the  harmony  be- 
tween accommodation  and  convergence.  For  every  di- 
optre of  accommodation  for  distance  there  is  developed 
nearly  two  degrees  (of  arc)  of  pseudo-esophoria,  which 
would  be  measured  by  a  prism  of  nearly  four  degrees. 
In  the  discussion  of  pseudo-esophoria  this  distinction  be- 
tween arc  and  prism  degrees  was  not  made;  hence  the 
author  would  emphasize  it  here.  Wherever  the  quantity 
of  pseudo-esophoria  is  given  in  the  chapter  on  esophoria, 
it  should  be  read  "of  arc,"  or  it  should  be  multiplied  by 
two  to  read  "of  prism." 

In  manifest  hyperopic  astigmatism,  simple  or  com- 
pound, the  guiding  sensation  must  be  satisfied  when 
Miiller's  muscle  has  so  accommodated  as  to  place  the 
focal  interval  on  the  macula,  for  vision  of  astigmatics  is 


646  MUSCLES   OF    THE   CILIARY   BODY. 

best  for  all  parts  of  an  object  when  the  anterior  focus 
is  just  as  far  in  front  of  the  retina  as  the  posterior  focus 
is  behind  it.  This  is  shown  in  the  half-tone  cut  on 
page  434.  However,  the  muscle  can  accommodate  so 
as  to  place  either  the  anterior  or  the  posterior  focus  on 
the  macula — in  the  first  instance,  sharpening1  lines  at 
right  angles  to  the  meridian  that  is  most  curved;  in  the 
second  instance,  sharpening  lines  that  are  parallel  with 
the  most  curved  meridian.  This  irregular,  zigzag  con- 
traction of  Miiller's  muscle  is  what  occurs  when  hyper- 
opic  astigmatic  eyes  look  at  checked  goods — a  very  un- 
pleasant thing  for  them  to  do. 

This  work  of  Miiller's  muscle — to  sharpen  images  in 
hyperopia  and  hyperopic  astigmatism — is  abnormal,  and 
always  develops  a  pseudo-esophoria.  The  pseudo-eso- 
phoria  manifests  itself  in  one  of  three  ways:  First,  it 
shows  an  esophoria,  when,  intrinsically,  there  is  ortho- 
phoria;  second,  it  shows  a  greater  amount  of  esophoria 
than  really  exists;  third,  it  lessens  an  existing  intrinsic 
exophoria.  In  either  instance,  if  the  muscle  of  accom- 
modation is  not  of  subnormal  development,  the  pseudo- 
esophoria  will  be  the  same  in  both  far  and  near  vision. 

In  any  case  of  hyperopia  or  hyperopic  astigmatism, 
the  error  must  be  considered — not  wholly  with  reference 
to  the  muscle  of  Miiller,  but  the  inherent  condition  of 
the  lateral  recti  muscles  must  also  be  taken  into  consid- 


MUSCLES   OF    THE   CILIARY   BODY.  647 

eration.  If  there  is  lateral  orthophoria,  and  especially  so 
if  there  is  an  inherent  esophoria,  the  abnormal  work  re- 
quired of  the  muscles  of  accommodation  should  be  re- 
lieved by  a  full  correction  of  the  focal  error,  and  the 
lenses  should  be  worn  for  both  far  and  near  seeing.  If 
there  is  inherent  exophoria,  it  would  be  better,  in  many 
cases,  especially  those  having-  strong-  muscles  of  accom- 
modation, to  correct  the  hyperopic  astigmatism  with 
minus  cylinders,  and  to  leave  uncorrected  any  low  de- 
gree of  hyperopia,  in  order  that  the  pseudo-esophoria 
may  neutralize,  wholly  or  in  part,  the  inherent  exo- 
phoria. In  every  case  of  hyperopic  astigmatism  a  full 
correction  of  all  the  error  that  can  be  made  manifest 
should  be  given,  using  either  plus  or  minus  cylinders,  as 
might  be  indicated  by  an  associated  study  of  the  focal 
error  and  the  intrinsic  state  of  the  muscles.  If  minus 
cylinders  are  used  because  of  a  complicating  exophoria, 
the  hyperopic  astigmatism,  which  is  worse,  is  converted 
into  a  simple  hyperopia,  which  is  better.  How  to  deal 
directly  with  any  inherent  muscle  imbalance,  has  already 
been  set  forth  in  preceding  chapters. 

MYOPIA  AND  MYOPIC  ASTIGMATISM. — When  either 
of  these  errors  exists,  the  guiding  sensation  does  not  call 
on  Miiller's  muscle  to  do  any  work  when  the  object  of 
fixation  is  in  the  distance.  If  there  is  simple  myopia  of 
3.  JD,  or  more,  the  muscle  of  accommodation  is  not  called 


648  MUSCLES   OF    THE   CILIARY    BODY. 

into  action,  even  in  the  near  use  of  the  eyes;  so  that  in 
such  eyes  the  muscle  remains  inactive,  whatever  may  be 
the  location  of  the  point  of  view,  unless  it  should  be 
brought  nearer  the  eyes  than  their  far  points.  If  there 
is  manifest  myopic  astigmatism,  the  accommodative  mus- 
cle will  be  brought  into  activity  only  when  the  eyes  are 
used  in  near  vision  and  for  the  purpose  of  placing  the 
focal  interval  on  the  macula.  In  compound  myopic  as- 
tigmatism, the  myopia  being  3.  D  or  more,  the  muscle  of 
Miiller  will  remain  inactive,  regardless  of  whether  the 
eyes  are  being  used  either  in  the  far  or  in  the  near.  In 
nryopia  of  less  than  3.  D,  with  the  page  at  thirteen  inches, 
the  guiding  sensation  calls  only  for  such  accommodative 
action  as  will  increase  the  refractive  power  of  the  lens 
to  correspond,  in  dioptres,  with  the  difference  between 
the  number  of  dioptres  of  myopia  and  3.  D.  This  work 
of  the  ciliary  muscle — to  improve  vision  in  the  near  when 
there  is  myopic  astigmatism,  and  to  give  the  proper  near 
point  when  there  is  a  low  degree  of  myopia — is  abnormal 
work,  though  less  than  is  required  when  there  is  emme- 
tropia.  These  refractive  errors  interfere  in  no  way  with 
any  intrinsic  muscle  condition,  when  the  point  of  view  is 
in  the  distance;  but  in  the  near  use  of  the  eyes  there  is 
a  resultant  pseudo-exophoria.  This  may  show  itself  in 
any  one  of  three  ways:  First,  there  will  be  an  exophoria 
in  the  near,  when,  intrinsicall)',  the  lateral  muscles  may 


MUSCLES   OF    THE    CILIARY    BODY. 

be  well  balanced;  second,  the  manifest  exophoria  will  be 
more  than  the  real;  third,  the  pseudo-exophoria  may 
serve  to  lessen  an  inherent  esophoria. 

In  any  case,  a  full  correction  of  a  myopic  error  for  the 
purpose  of  distant  seeing-  should  be  given,  since  such  a 
correction  will  not  excite  into  activity  the  muscle  of  ac- 
commodation, nor  will  it  interfere  with  any  existing 
state  of  the  lateral  muscles.  There  can  arise  no  disad- 
vantage from  wearing  the  correcting  lenses  for  distant 
vision,  and  there  is  a  very  great  source  of  pleasure  given 
in  making  sharp  and  well  defined  objects  that  are  re- 
mote. When  the  associated  muscle  condition  is  inherent 
orthophoria,  and  especially  when  there  is  exophoria  in 
the  near,  myopes  should  wear  their  correcting  lenses  for 
both  far  and  near  seeing;  but  when  there  is  esophoria, 
as  will  be  shown  in  both  the  distant  and  the  near  tests, 
the  myope  will  have  added  comfort  by  removing  his 
lenses  for  all  near  work,  in  that  the  pseudo-exophoria 
will  lessen  the  intrinsic  esophoria.  In  all  cases,  myopic 
astigmatism  should  be  corrected  by  a  proper  minus  cyl- 
inder when  there  is  lateral  orthophoria  or  exophoria  in 
the  near,  but  by  plus  cylinders,  to  be  worn  only  in  read- 
ing or  in  other  near  work,  when  there  is  a  complicating 
esophoria.  So  it  appears  that  myopic  errors  must  be 
studied  and  treated  by  taking  into  consideration  the 
Miiller  muscle  and  the  lateral  recti  muscles. 


650  MUSCLES   OF    THE   CILIARY    BODY. 

WEAKNESS  OF  MULLER'S  MUSCLE.  —  As  already 
shown,  the  amplitude  of  accommodation  diminishes  with 
advancing-  years.  Whether  this  failing  accommodation 
is  due  to  loss  of  power  in  the  muscle,  or  whether  it  is 
because  the  lens,  growing-  more  dense,  continually  suf- 
fers loss  of  elasticity,  is  still  a  subject  for  discussion. 
Probably  the  two  conditions  enter  as  factors  in  the  de- 
velopment of  presbyopia.  The  weakening-  of  the  muscle 
of  accommodation  may  favor  the  loss  of  elasticity,  and 
the  loss  of  elasticity  may  react  on  the  weak  muscle. 
Presbyopia  shows  itself  in  a  recession  of  the  near  point 
until,  finally,  it  has  been  removed  inconveniently  far. 
Before  this,  however,  the  muscle  may  have  become  so 
weak  that  its  use  in  reading-  or  other  near  work  bring-s 
on  fatig-ue,  headache,  or  other  symptoms  of  eye-strain. 
In  such  cases  one  of  two  thing's  should  be  done:  The 
muscle  should  be  helped  by  increasing  its  strength  by 
exercise,  or  by  supplementing  its  power. 

Can  presbyopia  be  deferred  ?  What  the  author  wrote 
in  1894,  in  answer  to  this  question,  so  perfectly  coincides 
with  his  present  views,  that  he  reproduces  it  here: 

' '  That  the  leading  cause  of  old  sight  is  failure  of  cil- 
iary power  we  think  may  be  proved;  and  if  this  is  true, 
simple  and  scientific  means  for  deferring  the  onset  of 
presbyopia  may  be  brought  into  use.  Rhythmic  exer- 
cise can  be  as  readily  effected  in  the  ciliary  muscle  as  in 


MUSCLES   OF    THE    CILIARY    BODY.  651 

any  of  the  extra-ocular  muscles.  Will  this  exercise  de- 
velop the  power  of  these  muscles  that  are  under  the 
direct  control  of  the  guiding  sensation,  the  common 
master  of  all  the  ocular  muscles  ? 

"That  involuntary  muscular  fibers  can  be  increased 
in  size  and  augmented  in  power  as  a  result  of  effort  to 
overcome  obstruction  is  a  matter  of  common  accept- 
ance, so  far  as  the  heart  and  the  bladder  are  concerned. 
In  mitral  stenosis  it  is  well  known  that  the  walls  of  the 
left  auricle  become  hypertrophied  and  more  powerful,  so 
that  it  may  send  the  blood  through  the  narrowed  open- 
ing into  the  ventricle;  in  like  manner,  when  there  is 
obstruction  at  the  aortic  opening,  the  walls  of  the  ven- 
tricle become  hypertrophied  and  more  powerful. 

"When  the  prostate  gland  is  enlarged  or  there  is 
stricture  of  the  urethra,  impeding  the  flow  of  urine,  the 
muscular  fibers  in  the  walls  of  the  bladder  are  increased 
in  size,  and  become  much  more  powerful,  so  as  to  be 
able  to  force  the  flow.  It  will  be  conceded  that  this 
muscle  development  in  heart  and  bladder  results  from 
effort  to  overcome  obstruction. 

"Displacement  of  images  by  prisms  and  blurred  im- 
ages by  means  of  concave  lenses  are  obstructions  which, 
if  not  too  great,  will  be  overcome  by  muscular  action— 
the  former,  by  action  of  the  recti  muscles;  the  latter,  by 
action  of  the  ciliary  muscles.  Many  observers  have 


652  MUSCLES   OF    THE   CILIARY   BODY. 

already  acknowledged  that  rhythmic  exercise  of  the 
recti  muscles,  by  means  of  prisms,  and  of  the  obliques, 
by  means  of  cylinders  properly  placed,  not  only  in- 
creases their  power,  but  at  the  same  time  dispels  the 
nervous  phenomena  associated  with  and  dependent  on 
their  former  weakness.  If  the  ciliary  muscles  can  be 
developed  by  rhythmic  exercise,  then  concave  lenses, 
not  too  strong1,  used  rhythmically,  but  not  too  long-  at  a 
time,  may  be  the  means  of  deferring  old  sight  to  five  or 
ten,  or  even  more,  years  beyond  the  now  common  age  of 
its  onset — about  the  age  of  forty-five  years. 

"As  in  developing  the  recti  and  obliques,  so  in  the 
development  of  the  ciliary  muscles,  the  power  to  over- 
come obstruction  should  never  be  taxed  to  anything  like 
its  fullest  capacity.  Gentle  contraction  and  relaxation, 
rhythmic  in  order,  continued  from  five  to  ten  minutes  and 
repeated  once  or  twice  every  twenty-four  hours,  must 
result  in  giving  tone  to  the  ciliary  muscles.  The  time 
of  life  for  beginning  the  exercise,  and  the  strength  of 
concave  lenses  to  use,  are  matters  that  must  be  settled 
by  observation  and  experience.  As  a  preliminary  to  the 
treatment  of  failing  accommodation,  all  existing  focal 
errors  should  be  corrected,  and  this  correction  should  be 
worn  behind  the  exercise  lenses  at  each  sitting.  A  mi- 
nus .50  D.  spherical  lens,  properly  centered,  will  be  the 
most  useful.  The  patient  should  be  seated  from  fifteen  to 


MUSCLES   OF    THE    CILIARY    BODY.  653 

twenty  feet  from  a  lighted  candle,  lamp,  or  gas  jet,  and 
should  look  at  the  same  through  the  concave  lenses  five 
seconds,  and  then  raise  them  for  a  period  of  five  seconds, 
and  so  on  to  the  end  of  the  sitting.  It  is  evident  that, 
with  the  focal  correction  on  when  needed,  the  image  of 
the  flame  is  sharp,  satisfying  the  guiding  sensation 
without  ciliary  action.  The  moment  the  weak  concave 
lenses  are  lowered  the  image  is  blurred,  and  at  once  the 
ciliary  muscles  are  called  into  action,  to  again  return  to  a 
state  of  rest  the  moment  they  are  raised.  Thus  contrac- 
tion and  relaxation  are  easily  induced.  In  this  way  the 
nutrition  of  the  muscle  should  be  improved  and  its 
power  enhanced  or  maintained.  The  age  at  which  to 
begin  the  exercise,  as  a  rule,  need  not  be  under  forty 
nor  over  forty-three  years,  and  it  should  be  continued  as 
long  as  the  proper  reading  distance  is  preserved. 

"The  question  would  naturally  arise  in  the  mind  of 
the  patient  as  well  as  that  of  the  practitioner:  '  Can  any 
injury  come  from  the  treatment?'  The  nutrition  of  the 
ciliary  body  is  from  the  blood  that  circulates  in  it. 
Nothing  is  more  reasonable  than  that  gentle,  rhythmic, 
and  periodic  exercise  of  the  ciliary  muscle  would  im- 
prove the  nutrition  of  the  ciliary  body,  just  as  the  nutri- 
tion of  other  muscles  is  improved  by  proper  exercise. 
No  harm,  then,  could  come  to  the  muscle  as  a  result  of 
the  proposed  gymnastic  exercise.  May  we  fear  unfa- 


654  MUSCLES   OF    THE   CILIARY   BODY. 

vorable  change  in  the  lens  as  a  consequence  of  this  exer- 
cise of  the  ciliary  muscle  ?  It  is  generally  conceded  that 
the  lens  gets  its  nourishment,  by  the  process  of  osmosis, 
from  the  blood  circulating  in  the  ciliary  body.  It  must 
be  acknowledged  that  the  better  the  nutrition  of  the 
lens,  the  more  likely  will  it  retain  its  two  very  impor- 
tant properties,  transparency  and  elasticity.  It  cannot 
be  denied  that  the  better  the  nutrition  of  the  ciliary 
body,  the  healthier  will  be  the  crystalline  lens.  We 
must  conclude  that,  if  the  exercise  would  improve  the 
condition  of  the  ciliary  body,  it  would  at  the  same  time 
have  a  tendency  to  improve  the  nutrition  of  the  lens, 
whereby  the  latter  would  be  only  the  more  certain  to 
continue  both  transparent  and  elastic.  Thus  not  only 
may  old  sight  be  deferred,  but  also  the  development  of 
cataract  may  be  prevented." 

It  is  now  about  eight  years  since  the  above  was  writ- 
ten. During  five  of  these  years,  beginning  at  the  age  of 
forty-three  years,  the  author  faithfully  "took  his  own 
prescription,"  hardly  a  day  passing  that  he  did  not  exer- 
cise his  ciliary  muscles  with  concave  spheres.  When  the 
exercise  was  commenced,  there  was  already  beginning 
presbyopia,  interfering  somewhat  with  the  finding  of 
foreign  bodies  in  the  cornea  and  with  their  removal. 
There  was  hesitating  vision  in  the  more  delicate  opera- 
tion on  the  eye.  He  commenced  the  exercise  with  a  mi- 


MUSCLES   OF    THE    CILIARY   BODY.  655 

nus  .50  sphere  and  soon  experienced  increase  of  ciliary 
power,  as  shown  in  both  comfort  and  convenience  experi- 
enced in  reading1  and  operative  work.  After  a  few  months 
a  minus  1.  sphere  was  substituted  for  the  weaker  lens, 
and  with  this  the  exercise  was  continued  until  the  age  of 
forty-eight  years.  Except  for  the  hard  work,  by  artifi- 
cial light,  incident  on  the  writing  of  this  book,  he  would 
have  continued  the  exercise  longer,  possibly  until  the 
age  of  fifty  years.  Even  now,  in  his  forty-ninth  year, 
although  he  has  been  wearing  a  presbyopic  lens  (a 
plus  1.  D)  for  the  past  six  months,  he  can  see  to  read  this 
print  easily  at  fifteen  inches  through  his  astigmatic  cor- 
rection only.  If  the  three  necessary  factors  for  carry- 
ing out  this  exercise — time,  patience,  and  perseverance — - 
could  be  kept  compounded,  much  might  be  accomplished, 
especially  if  the  exercise  were  commenced  before  the 
age  of  forty  years. 

If  the  exercise  treatment  is  not  resorted  to,  waning 
ciliary  power  should  be  supplemented  by  convex  lenses, 
as  soon  as  inconveniences  arise  in  near  work.  There  is 
no  reason  why  plus  .50  D  spheres  might  not  be  first  used, 
and  as  long  as  they  give  comfort.  Whenever  the  ciliary 
muscles  begin  to  call  for  more,  the  presbyopic  correction 
should  be  increased  by  steps  of  .50  D.  Finally,  when  all 
ciliary  power  has  vanished,  artificial  aid  must  be  sub- 
stituted for  the  lost  ciliary  power.  To  give  an  unneces- 


656  MUSCLES   OF    THE   CILIARY   BODY. 

sarily  strong  presbyopic  correction  at  the  beginning 
should  be  avoided,  for  by  so  doing  the  nutrition  of  both 
the  ciliary  body  and  the  lens  might  be  interfered  with. 
Presbyopic  lenses  should  always  be  correctly  centered, 
and  they  should  be  set  before  the  eye  so  that  the  visual 
axes  would  pass  through  the  lenses  at  right  angles. 

WEAKNESS  OF  MULLER'S  MUSCLE  IN  THE  YOUNG. 
— Either  from  the  want  ol  proper  development  of  the 
muscles  or  because  of  faulty  innervation,  the  power  of 
accommodation  in  young  people  is  often  found  below 
par.  In  association  with  convergence,  the  printed  page 
may  be  seen,  but  prolonged  use  of  the  eyes  for  reading 
fatigues  the  weak  muscles  and  brings  on  headache  or 
other  reflex  nervous  symptoms.  If  focal  errors  exist  in 
these  cases,  they  should  be  corrected  as  might  be  indi- 
cated by  an  associated  study  of  the  focal  errors  and  in- 
trinsic condition  of  the  lateral  recti  muscles.  In  many 
cases  weakness  of  Miiller's  muscle  is  the  chief  source 
of  trouble;  and  if  comfort  is  ever  to  be  given  such  a  suf- 
ferer, this  condition  must  be  treated. 

A  diagnosis  of  such  a  condition  may  be  made  easily  by 
means  of  the  concave  lenses  in  the  refraction  case,  but 
more  easily  and  rapidly  by  means  of  two  parallel  bars 
containing  a  series  of  concave  spherical  lenses,  varying 
in  strength  from  .50  to  3.  D,  the  difference  in  strength 
between  any  two  adjacent  lenses  being  .50  D.  These 


MUSCLES   OF    THE    CILIARY   BODY.  657 

bars  should  be  so  connected  above  that  the  distance 
between  them  may  be  regulated  to  suit  the  distance 
between  the  pupillary  centers  of  the  eyes  to  be  tested. 
The  minus  .50  should  be  below;  the  minus  .3D  sphericals, 
above.  Beginning  with  minus  .50  sphericals  before  the 
two  eyes,  the  patient  all  the  while  looking  at  the  Snellen 
letters  made  to  be  read  at  twenty  feet,  each  pair  of  lenses 
should  be  passed  down  in  front  of  the  eyes  so  long  as 
the  patient  is  still  able  to  see  xx-  If  the  muscles  of  ac- 
commodation are  weak,  ciliary  power,  unassociated  with 
convergence,  will  be  less  than  3.  D;  in  many  cases  it  is 
not  more  than  1.  D.  The  standard  of  ciliary  power,  when 
unassociated  with  convergence,  may  be  placed  at  3.  D,  for 
the  reason  that  a  ciliary  muscle  that  can  overcome  a 
minus  3.  D,  when  not  converging,  can  easily  accommodate 
for  the  reading  distance,  in  association  with  convergence. 
Not  much  help,  from  a  diagnostic  standpoint,  can  come 
from  a  test  of  the  relative  power  of  accommodation. 
The  test  apparatus  just  described  may  be  called  a  "cili- 
ometer. "  Except  for  the  trouble  and  inconvenience,  the 
lenses  from  the  trial  case  could  be  used  for  making  these 
tests. 

Lucien  Howe  has  devised  a  more  complicated  appa- 
ratus for  testing  ciliary  power,  which  he  exhibited  before 
the  Section  of  Ophthalmology  of  the  American  Medical 
Association  two  or  three  years  ago.  As  the  author  re- 


658  MUSCLES   OF    THE   CILIARY   BODY. 

members  the  device,  he  thinks  it  would  be  easy  to  use 
and  fully  worthy  of  trust. 

Every  protracted  illness  must  weaken  ciliary  power, 
which  time  and  tonics  will  relieve.  Such  patients  should 
abstain  from  near  work  until  the  general  health  has 
been  fully  restored 

TREATMENT. — The  treatment  of  weakness  of  Miil- 
ler's  muscle  is  by  exercise,  after  the  method  set  forth  in 
the  answer  to  the  question:  "Can  presbyopia  be  de- 
ferred?" The  result  of  the  exercise  will  depend  largely 
on  the  faithfulness  with  which  it  is  carried  out.  In 
cases  of  congenital  weakness  of  the  ciliary  muscles, 
strychnia,  electricity,  and  other  tonics  can  accomplish 
but  little.  Rhythmic  exercise  by  means  of  minus  .50  to 
minus  1  D  spherical  lenses  will  cure,  usually  in  a  few 
months.  The  giving  of  convex  lenses  to  supplement 
the  weak  ciliary  power  should  not  be  considered,  for  it 
would  be  making  the  patient  old  while  yet  young. 

BOWMAN'S  MUSCLE:  ITS  NORMAL  AND  ABNORMAL 
WORK. — In  non-astigmatic  eyes,  when  the  position  of 
the  lens  is  ideal  from  the  processes  of  development,  the 
Bowman  muscle  can  have  nothing  to  do,  unless  it  be  to 
aid  in  steadying  the  lens  in  the  act  of  accommodation  by 
Miiller's  muscle.  Such  action,  if  it  occurs,  must  be  of 
the  entire  muscle. 

If  a  lens,  as  the  result  of  the  processes  of  develop- 


MUSCLES   OF    THE    CILIARY    BODY.  659 

ment,  is  not  ideally  placed  in  a  non-astigmatic  eye — es- 
pecially if  its  equatorial  plane  is  not  parallel  with  the 
equator  of  the  eye,  and  probably  if  its  antero-posterior 
axis  does  not  coincide  with  the  visual  axis — the  task  of 
correction  of  these  errors  must  fall  on  Bowman's  muscle, 
and  the  work  must  be  accomplished  through  the  guiding 
sensation  of  the  retina,  most  likely  in  the  earlier  months 
of  infancy.  This  regulation  of  position  must  be  effected 
by  action  of  a  definite  portion  of  the  muscle,  and  it  must 
be  kept  up  unless  the  suspensory  ligament  should  un- 
dergo such  change  as,  in  itself,  would  fix  the  lens.  A 
failure  on  the  part  of  the  muscle  to  act  would  give  a 
permanent  lenticular  astigmatism.  Such  work  required 
of  Bowman's  muscle  would  be  abnormal,  but  essential. 

When  there  is  corneal  astigmatism,  there  is  necessity 
for  abnormal  action  of  Bowman's  muscle  in  a  localized 
part.  The  adjustment  of  the  lens  must  be  such  as  to 
increase  its  refractive  power  in  the  part  at  right  angles 
to  the  plane  of  the  meridian  of  greatest  curvature  of  the 
cornea.  This  can  be  effected  in  one  of  two  ways — first, 
by  a  contraction  of  one  single  part  of  Bowman's  muscle, 
so  as  to  rotate  the  lens  on  an  axis  that  lies  in  the  plane 
of  the  meridian  of  the  cornea  that  is  most  curved;  second, 
by  the  simultaneous  and  equal  contraction  of  opposite 
parts  of  the  muscle  so  as,  by  pressure  on  the  lens  through 
the  tension  of  corresponding  parts  of  the  suspensory 


660  MUSCLES   OF    THE    CILIARY   BODY. 

ligaments,  to  increase  the  curvature  of  that  part  of  the 
lens  at  right  angles  to  the  plane  of  the  most  curved  cor- 
neal  meridian.  While,  in  either  instance,  the  corneal  as- 
tigmatism would  be  neutralized,  in  part  or  wholly,  the 
author  inclines  to  the  view  that  it  is  effected  by  the  tilt- 
ing- of  the  lens.  This  work  is  abnormal,  rarely  ever 
perfectly  effective,  especially  in  the  higher  degrees  of 
astigmatism,  and  is  probably  one  of  the  worst  kinds  of 
eye-strain.  As  the  patient  grows  older  this  astigmatic 
accommodative  power  is  less  able  to  accomplish  its  work, 
and  a  greater  amount  of  the  astigmatism  becomes  mani- 
fest. There  is  no  known  drug  that  will  suspend  astig- 
matic accommodation,  else  at  the  first  examination  the 
whole  error  could  be  found,  and  should  be  corrected. 

There  are  but  two  ways  to  deal  with  astigmatism: 
First,  correct  only  the  manifest  error,  increasing  the 
strength  of  the  cylinder  from  time  to  time,  as  the  latent 
error  becomes  manifest;  second,  give  at  once  a  full  cor- 
rection of  the  corneal  astigmatism,  as  shown  by  the  oph- 
thalmometer,  and  thus  force  the  suspension  of  the  ac- 
commodative astigmatic  power,  which  would  doubtless 
occur  in  a  short  while. 

The  production  of  artificial  astigmatism,  unless  indi- 
cated by  insufficiency  of  the  superior  obliques,  should 
always  be  avoided.  To  avoid  thus  calling  into  abnor- 
mal action  any  part  of  Bowman's  muscle,  the  correction 


MUSCLES   OF    THE   CILIARY   BODY.  661 

of  corneal  astigmatism  should  be  perfect,  both  as  to 
strength  of  cylinder  and  location  of  its  axis;  and  when 
minus  spherical  lenses  are  required  for  the  correction  of 
myopia,  or  plus  spherical  lenses  are  given  for  the  cor- 
rection of  hyperopia  and  presbyopia,  they  should  be  so 
placed  that  the  plane  of  each  lens  shall  be  parallel  with 
the  equator  of  the  eye  by  which  it  is  to  be  used. 


APPENDIX. 


In  the  original  Cyclo-phorometer,  depicted  on  page  262, 
the  graduated  semicircle  is  below.  Those  now  made 
have  the  degrees  marked  in  the  semicircle  above.  In  the 
former  instrument,  when  the  index  stands  in  the  lower- 
nasal  arc,  in  order  to  make  the  two  streaks  of  light  paral- 
lel, the  condition  is  plus  cyclophoria;  in  the  latter  instru- 
ment, when  the  index  stands  in  the  upper-temporal  arc, 
the  condition  is  plus  cyclophoria.  In  either  instrument, 
when  testing  for  cyclophoria  or  cyclotropia,  the  upper- 
temporal  and  lower-nasal  arcs  refer  to  the  superior 
obliques,  and  the  upper-nasal  and  lower-temporal  arcs 
refer  to  the  inferior  obliques. 

The  duction  arcs  for  the  superior  obliques  are  the 
upper-nasal  and  lower-temporal;  for  the  inferior  obliques, 
the  upper-temporal  and  lower-nasal. 


INDEX. 


ANTAGONISTS  AND  SYNERGISTS, 

tables  of    59,    62 

ADVANCEMENT  OPERATION, 

to  only  alter  tension  261 

to  alter  tension  and  change  plane 266 

marginal  267 

for  esophoria 312 

suggested  by  Querin  501 

of  Lagleize 269 

ABEA,  RETINAL, 

of  binocular  fusion,  and  how  measured  175 

ANGLE  GAMMA 528 

how  measured 532 

Axis  OF  CARDINAL  ROTATIONS, 

how  to  find 16 

AXES  OF  OBLIQUE  ROTATIONS, 

are  only  two  44 

ACTION, 

principal  and  subordinate,  of  a  muscle 52 

ASTIGMATISM, 

oblique,  why  more  annoying  than  the  vertical  446 

parallel   450 

phenomena  of,  shown  by  experiments 459 

metamorphopsia  in,  through  correcting  cylinders  462 

hyperopic,  how  to  correct  647 

myopic,  how  to  correct 649 

(662) 


INDEX.  663 

ASTIGMATIC  ACCOMMODATION   637,  638 

two  points  about   639 

ANISOMETROPIA, 

a  cause  of  compensating  hetcrotropia 492 

ANTIPATHY 

to  binocular  single  vision,  explained 520 

ACCOMMODATION  AND  CONVERGENCE  279 

Axis  OF  VISION  6,  8 

Axis  OF  ROTATION  8 

ACCOMMODATION, 

change  of  lens  in 629 

Helmholtz'  theory  of 630 

muscle  of  631 

Miiller's  or  Bowman's,  which?   632 

Tscherning's  views  of  lens-changes  in 632 

presbyopic  correction  compared  with   633 

of  the  hyperope 633 

conclusions  about 635 

normal  power  of,  how  determined  657 

ABDUCENS  597 

ADDUCTION, 

the  normal 153,  158,  197 

ABDUCTION, 

the  normal  153,  158,  197 

ADVERSION  169,  173,  201 

ABVERSION  168,  172,  201 

ADJUSTMENT  OF  CYLINDERS  486 

BAXTEB'S  CYCLO-PHOROMETER  161 

BLACK  268 

BREWER'S  TORSIOMETER  161 

BEARD 2G8 

BERGER  .  G2 1 


664  INDEX. 

BIFFI 625 

BINOCULAB  SINGLE  VISION 104,  105 

line   (curve)  of  99,  102 

surface  of    99 

antipathy  to 520 

BINOCULAB  ROTATIONS, 

in  the  four  cardinal  directions 7,  21 

in  oblique  directions   ^     58 

BINOCULAB  FUSION  FIELD 174 

BINOCULAB  FIELD  OF  VISION 125 

BINOCULAB  FIELD  OF  VIEW  125 

BINOCULAB  SPACIAL  POLE 124,  135 

BINOCULAB  SPACIAL  MERIDIANS 126,  131 

BINOCULAB  SPACIAL  PARALLELS 130 

BRAIN  CENTERS  FOR  BINOCULAR  ROTATIONS, 

how  they  control  77,78 

demonstration  of  their  existence  78-81 

individual  fusion  centers   81 

BROWN,  MANNING 99 

BOWMAN'S  MUSCLE 628 

nerve  supply  of 635 

function  of 636 

how  it  may  act 640 

its  normal  and  abnormal  work 658 

its  work  of  adjusting  the  lens,  after  birth 659 

its  work  in  neutralizing  corneal  astigmatism 659 

BURNETT,  SWAN  M 185,  402,  638 

CARDINAL  ROTATIONS  169 

CATAPHORIA, 

treatment  of,  by  prisms   233 

<  See  "  Hyperphoria.") 


INDEX.  665 

CATAPHORIA,  DOUBLE, 

causes  of 353 

treatment  of, 

by  prisms  376 

by  exercise  378 

by  operations 378 

CATATROPIA,  DOUBLE, 

without  cyclotropia 581 

•with  plus  cyclotropia  581 

the  operations  for  585 

with  minus  cyclotropia 581 

CENTERS, 

the  conjugate 69,  70 

the  fusion 71,  80-91 

CHECK  LIGAMENTS 503 

CHECKED  GOODS, 

why  annoying  to  astigmatics   646 

CILIARY  MUSCLES, 

normal  and  subnormal 281 

super-normal    282 

CILIARY  BODY, 

muscles  of  628 

Bowman's    628 

Miiller's 629 

CILIOMETER 657 

CHISOLM,  J.  J 329 

CRITCHETT  502 

CONJUGATE  CENTERS, 

disease  of  sixth,  seventh,  eighth,  and  ninth  612 

disease  of  first,  second,  third,  fourth,  and  fifth  614 

COLLINS    624 

Coccius   .  631 


666  INDEX. 

CONJUGATE  INNERVATIONS 69,  70 

CORRESPONDING  RETINAL  POINTS  451 

CONVERGENCE, 

angle  of,  and  formula  for  calculating 140 

angle  of,  and  pupillary  distance 141 

size  of  angle  of,  how  to  find 144 

CONVERGENCE  AND  ACCOMMODATION  279 

CORNEA, 

decentration  of 493 

imperfect  images  caused  by 494 

how  to  detect 494 

CROSS-EYES 497 

CULBERTSON,  H 401,  407 

CYCLO-PHOROMETER   161 

how  to  use 162 

CYCLO-DUCTION 163,  167,  198,  396 

CYCLOPHOHIA, 

history  of 383 

varieties  of 384 

causes  of 384 

tests  for, 

by  Maddox  prism  194,  389 

by  single  prism 194,  392 

by  rotary  prism  392 

by  the  Stevens  clinoscope 195,  393 

by  the  cyclo-phorometer  195,  395 

symptoms  of  400 

treatment  of, 

by  exercise  cylinders  237,  401 

by  rest  cylinders 402 

how  to  place  axes  of  cylinders  given  for  correction  of  astigma- 
tism      405 

by  operations 248,  414 


INDEX.  667 

CYCLOPHOBIA, 

operations  for,  first  suggested  402 

uncomplicated, 

the  operations  for  414 

complicated  by  double  hyperphoria, 

the  operations  for  414 

complicated  by  double  cataphoria, 

the  operations  for  414 

complicated  by  right  hyperphoria  and  left  cataphoria, 

the  operations  for  414 

complicated  by  sthenic  esophoria, 

the  operations  for  414 

complicated  by  sthenic  exophoria, 

the  operations  for  414 

complicated  by  esophoria,  right  hyperphoria,  and  left  catapho- 
ria, 

the  operations  for  415 

complicated  by  exophoria,  right  hyperphoria,  and  left  catapho- 
ria, 

the  operations  for 415 

CYCLOTROPIA, 
compensating, 

history  of  the  study  of 419,  438 

caused  by  oblique  astigmatism  418 

how  retinal  images  are  displaced 439 

how  the  displaced  images  are  fused 442,  458 

treatment  of,  by  correcting  cylinders  466 

annoyances  following  treatment  of 466 

why  annoyances  vanish  sooner  in  some  cases  than  in  others. . .   467 

Lippincott's  method  of  applying  correcting  cylinders 469 

the  kind  of  cases  requiring  this  method 469 

the  kind  of  cases  not  requiring  this  method  471 

the  gradual  correction  of,  by  displacing  the  axes  of  the  fully 

correcting  cylinders 471 

Steele  rule  for  displacing  cylinders 472 

Steele  rule  corrected  .  472 


668  INDEX. 

CYCLOTBOPIA, 

comitant    587 

parallel  and  non-parallel  588 

parallel,  causes  of 588 

plus,  causes  of  589 

minus,  causes  of 589 

how  detected  and  measured  590 

plus, 

complicated  by  double  hypertropia, 

the  operations  for  591 

complicated  by  hypertropia  of  one  eye  and  catatropia  of  the 
other, 

the  operations  for  592 

uncomplicated, 

the  operations  for  593 

CYLINDERS, 

adjustment  of 486 

distortion  by  displacement  of  484 

DANIEL,  PBOF.  JOHN 48 

DEBCUM  AND  PABKEB'S  EXPERIMENTS  210 

DESCHWEINITZ  221 

DEADY 231 

DECENTBATION  OF  LENSES  302 

DEGREES. 

of  arc  and  of  prism  compared  643,  645 

DEVIATIONS, 

primary  and  secondary  525 

DJPLOPIA, 

Nature's  two  methods  of  preventing 66,  498 

DISTORTION  BY  CYLINDERS, 

arcs  of  474,  484 

plates  illustrating   475,  480,  485 

a  knowledge  of,  necessary 486 


INDEX.  669 

DlEFFENBACH    499 

BONDERS   279,  509 

DOAK,  R.  S 363 

DUANE    187 

DUNN,  JOHN 566 

DUCTION  POWER 197 

standard  of   176 

value  of 199 

how  determined  by  the  Wilson  phorometer  153 

how  determined  by  the  monocular  phorometer  157 

EXTERNUS. 

plane  of  action  of 53 

correct  attachment  of  53 

high  attachment  of  53 

low  attachment  of 53 

operation  on  (see  "  Exophoria  "  and  "  Esophoria.") 

EXERCISE, 

ceiling-to-floor  and  wall-to-wall    177 

EMMETROPIA, 

Miiller's  muscle  in    642 

convergence  and  accommodation  in  643 

with  orthophoria  643 

EXOPHORIA  314 

pseudo, 

causes  of 318 

treatment  of,  by  concave  lenses  328 

treatment  of,  by  under-correction  of  hyperopia  329 

intrinsic    315 

causes  of 315 

sthenic  and  asthenic 317 

why  variable 317 

tests  for, 

by  exclusion 322 


670  INDEX. 

EXOPHORIA,  314 

by  red  glass 323 

by  double  prism 323 

by  single  prism  323 

by  Maddox  rod  324 

by  photometer 324 

abduction,  and  abversion  in  325 

adduction  and  adversion  in  326 

complications  of 326 

symptoms  of  327 

treatment  of, 

by  prisms  for  constant  wearing 330 

by  exercise  prisms  230,  334 

by  candle  exercise  228,  332 

by  Gould  or  Deady  method  232 

how  to  adjust  rest  prisms  in 331 

sthenic,  uncomplicated, 

the  operations  for 336 

complicated  by  hyperphoria  and  cataphoria  only, 

the  operations  for  337 

complicated  by  plus  cyclophoria  only, 

the  operations  for  337 

complicated  by  hyperphoria  and  cyclophoria, 

the  operations  for  338 

asthenic,  uncomplicated, 

the  operations  for  338 

complicated  by  hyperphoria  and  cataphoria  only, 

the  operations  for 339 

complicated  by  cyclophoria  only, 

the  operations  for  339 

complicated  by  hyperphoria  and  cyclophoria, 

the  operations  for  339 

ESOPHOBIA, 

pseudo, 

cause  of 278 

how  it  manifests  itself  .  .   279 


INDEX.  671 

ESOPHOBIA, 

treatment  of 297 

intrinsic  or  inherent, 

conditions  that  cause  273 

sthenic,  how  determined   277 

asthenic,  how  determined  278 

tests  for,  when  unreliable   284 

by  exclusion    286 

by  red  glass 286 

by  double  prism  287 

by  single  prism  287 

by  Maddox  rod  288 

by  the  phorometer 291 

the  same,  far  and  near  281 

variable,  greater  in  the  far   280 

complications  of 293 

symptoms  of  294 

treatment  of, 

by  convex  lenses   297 

by  rest  prisms,  and  how  to  adjust 299 

by  exercise  prisms  233,  304 

sthenic,  uncomplicated, 

the  operations  for  308 

complicated  by  hyperphoria  and  cataphoria  only, 

the  operations  for  308 

complicated  by  cyclophoria  only, 

the  operations  for  309 

complicated  by  plus  cyclophoria  and   hyperphoria  of  one  eye 
and  cataphoria  of  the  other, 

the  operations  for  310 

asthenic,  uncomplicated, 

the  operations  for  310 

complicated  by  hyperphoria  and  cataphoria  only, 

the  operations  for  311 

complicated  by  plus  cyclophoria  only, 

the  operations  for  311 


672  INDEX. 

ESOTROPIA, 
comitant   513 

time  of  occurrence,  and  why  513 

causes  of 514 

esophoria  as  a  cause 515 

hyperopia  516 

hyperphoria  and  cataphoria  517 

low  visual  acuity       519 

faulty  connection  of  the  maculas  with  the  brain 520 

varieties  of  524 

tests  for, 

by  phonometer 520 

by  perimeter 531 

by  tape   533 

by  linear  method  535 

by  Hirschberg  method  535 

symptoms  of  536 

amblyopia  537 

disfigurement    538 

secondary  deviation   539 

headache  and  other  reflexes  536 

treatment  of  539 

by  convex  lenses 539 

why  these  should  be  given  only  540 

by  atropine  in  the  good  eye  543 

by  flap  before  the  good  eye 543 

by  the  stereoscope 544 

by  the  amblyoscope 545 

by  bar  reading  548 

the  object  of  treatment  544 

operative  treatment  of 549 

by  complete  tenotomies,  never  549 

why  Panas'  complete  tenotomy  is  safer  than  any  other 550 

by  advancements   551 

the  two  extremes  in  operating 551 

by  partial  tenotomies,   advancements,   and   shortenings,   the 
ideal  operations  552 


INDEX.  673 

ESOTROPIA, 

the  two  effects  that  may  be  accomplished  by  any  operation. . . .   552 
comitant,  uncomplicated, 

the  operations  for  553 

complicated  by  hypertropia  and  catatropia  only, 

the  operations  for  555 

complicated  by  plus  cyclotropia  only, 

the  operations  for  555 

complicated  by  plus  cyclotropia  and  hypertropia  of  one  eye  and 
catatropia  of  the  other, 

the  operations  for  556 

complicated  by  plus  cyclotropia  and  double  hypertropia, 

the  operations  for  558 

EXOTROPIA, 
comitant, 
causes  of, 

myopia 561 

exophoria    561 

defective  third  innervation  center  561 

the  obliques  may  cause  562 

traumatism  (bad  surgery  on  an  internus) 562 

is  a  binocular  trouble 563 

complications  of 563 

symptoms  of  564 

a  case  of  non-comitant,  with  symptoms  562 

comitant,  uncomplicated, 

the  operations  for 569 

complicated  by  hypertropia, 

the  operations  for  570 

complicated  by  plus  cyclotropia  only, 

the  operations  for 571 

complicated  by  plus  cyclotropia,  hypertropia,  and  catatropia, 

the  operations  for  572 

complicated  by  plus  cyclotropia  and  double  hypertropia, 

the  operations  for  574 

simple, 

the  Fox  operation  for 575 


674  INDEX. 

EYE, 

the  ideal   27-35 

the  non-ideal 27-35 

FBAMES  FOB  EXERCISE  CYLINDERS   411 

FIXED  PLANES  OF  THE  HEAD 72 

FIXATION,  LINE  OF  528 

Fox's  OPERATION  FOB  EXOTROPIA 575 

FUSION,  RETINAL  AREA  OF 175 

GBAEFE 184,  500,  520 

GAMMA,  ANGLE  528 

GOULD  231 

GUIDING  SENSATION 175,  641 

GBTTNHAGEN 624 

HALE,  G.  W 215 

HELMHOLTZ 10,  15,  16,  25,  96,  630 

HELMHOLTZ'  FUNDAMENTAL  ERRORS 14,  34 

HELMHOLTZ  AND  THE  AUTHOR, 

eight  points  of  disagreement  32-34 

HELMHOLTZ'  METHOD 

of  finding  the  fixed  axis  of  a  rotation  10-13 

HESS 635 

HETEROPHOBIA, 

vertical  180 

lateral    181 

oblique 181 

causes  of 181 

pseudo  and  intrinsic   188 

tests  for 188,  189 

symptoms  of 203 


INDEX.  675 

HETEROPHOP.IA, 

headache  204 

vertigo  and  nausea   206 

confubion  of  thought   206 

chorea    207 

epilepsy  208 

catalepsy  212 

hysteria  213 

neurasthenia   213 

visceral  disturbances    214 

asthenopia   216 

treatment  of, 

by  rest  prisms 217 

by  rest  cylinders   219 

by  exercise  prisms    220 

by  operations 239 

HETEROTROPIA, 

compensating    489 

caused  by  anisometropia 489 

caused  by  prisms  and  decentered  lenses 492 

comitant, 

varieties  of 497 

history  of 499 

Panas'  operation  for  503 

classes  of  510 

treatment  of  (see  "  Esotropia,"  etc.) 

how  distinguished  from  paralytic  heterotropia 512 

HlRSCHBERG      538 

HOROPTER 35-39,  94 

HOTZ 419 

HOWE    657 

HYPERKIXESIS  AND  HYPOKIXESIS  .  .187 


676  INDEX. 

HYPEBPHOBIA  AND  CATAPHOETA, 
inherent, 
causes  of, 

malformation  of  orbits 342 

too  high  attachments  of  the  lateral  recti 349 

other  causes  350,  354 

tests  for   358 

proof  tests  for 361 

duction  and  version  tests  366 

complications  of 366 

symptoms  of 367 

tilting  of  head  in  363 

treatment  of, 

by  prism  exercise 233,  372 

by  rest  prisms 375 

uncomplicated, 

the  operations  for  379 

complicated  by  cyclophoria, 

the  operations  for  380 

HYPEBPHORIA,  DOUBLE, 

causes  of 351 

tests  for 361 

proof  tests  for  193,  361 

treatment  of, 

by  prisms  376 

by  straight-forward-to-floor  exercise  377 

by  operations   377 

HYPEBTBOPIA  AND  CATATROPIA  581 

with  no  cyclotropia 582 

with  cyclotropia  582 

the  causes  of 583 

symptoms  of   583 

treatment  of 584 

uncomplicated, 

the  operations  for   586 


INDEX.  677 

HYPEKTEOPIA  AND  CATATROPIA 581 

complicated  by  plus  cyclotropia, 

the  operations  for  586 

complicated  by  parallel  cyclotropia, 

the  operations  for 597 

HYPEBTBOPIA,  DOUBLE, 

without  cyclotropia 581 

with  minus  cyclotropia   581 

with  plus  cyclotropia  581 

uncomplicated, 

the  operations  for  584 

complicated  by  plus  cyclotropia, 

the  operations  for  585 

complicated  by  minus  cyclotropia, 

the  operations  for 585 

INTERNUS, 

correct  attachment  of 52 

high  attachment  of 52 

low  attachment  of 52 

plane  of 52 

operations  on  (see  "  Esophoria  "  and  "  Exophoria.") 

INFERIOR  OBLIQUE, 

plane  of 53 

INNEBVATIONS,  THE  CONJUGATE 69 

what  they  do 147 

IBIS, 

muscles  of  624 

nerves  of 626 

function  of 626 

weak  sphincter  of,  how  to  treat  627 

ISOGONAL  CIRCLES,  PRIMARY 104 

ISOGONAL  CIRCLES,  SECONDARY 105 

ISOGONAL  CIRCLE 94,  97,  102 


678  INDEX. 

ISOGONAL  SURFACE 99,  102 

IK  SUFFICIENCY  OF  THE  OBLIQUES 461 

JACKSON,  EDWABD 302 

JOHNSON,  W.  B 538 

JULER   625 

KNAPP 26,  501 

LAW, 

of  monocular  rotations   57 

of  binocular  rotations   109 

of  corresponding  retinal  points 64 

of  direction  65,  94 

of  direction  subordinate  to  the  law  of  corresponding  retinal 

points 456 

LAGLIEZE'S  OPERATION  269 

LAGOPHTHALMOS  618 

causes  of 620 

symptoms  of  618 

treatment  of 622 

LANDOLT   502,  554 

LAWRENCE  535 

LE  CONTE 35,  38,  94,  95 

LENS, 

changes  of,  in  accommodation  632 

effect  of  tilting  of  637 

elasticity  of,  how  suspended 642 

how  to  set  for  presbyopia  656 

LISTING'S  PLANE 75 

law  43 

LINES  OF  DIRECTION  35 

where  they  cross  31 

where  they  do  not  cross  27-30 


INDEX.  679 

LIPPINCOTT  469 

LOWBY    430 

MACULA,  THE  ROTATING  POINT  6 

MADDOX 46,  101,  102,  187,  302 

MADDOX  ROD 159 

its  legitimate  use  160 

single  in  testing  for  oblique  astigmatism,  but  multiple  when 
testing  for  cyclophoria 465 

MAY  303 

MAUNOIE   624 

MAYO   625 

MACULA, 

"  new-formed,"  so-called   496 

MEBIDIANS, 

retinal  17 

spacial,  monocular 17 

spacial,  binocular  126,  131 

METRE-ANGLE  OF  NAGEL 141 

variable  with  pupillary  distances 142 

value  of,  in  degrees 143 

METAMOEPHOPSIA  THROUGH  CORRECTING  CYLINDERS, 

cause  of 462 

why  it  disappears  more  quickly  in  some  cases  than  in  others. . .   462 

MICHEL,  CHARLES  E 226 

MONOSCOPTEB 94 

MOTOR  NERVES, 

the  third 595 

the  fourth 597 

the  sixth  597 

MUSCLES  ARRANGED  IN  NINE  PAIRS  .  68 


680  INDEX. 

MUSCLE  INDICATOR 113 

MUSCLE  PLANE, 

of  the  internus 52 

of  the  externus 53 

MULLEB'S  MUSCLE 629 

nerve  supply  of 635 

function  of 641 

loss  of  power  in  643 

table  showing  644 

in  emmetropia 642 

in  hyperopia   645 

in  hyperopic  astigmatism 645 

in  myopia 647 

in  myopic  astigmatism 648 

weakness  of,  in  the  old 650 

weakness  of,  in  the  young 652 

diagnosis  of 656 

treatment  of 658 

NAGEL 141 

NETTLESHIP ....'.... 407 

NODAL  POINT 27-35 

NOMENCLATURE  OF  THE  MUSCLES   185 

NOTES  222 

OPHTHALMOLPLEGTA  EXTERNA. 

symptoms  of  603 

causes  of 603 

OPERATIONS  ON  THE  MUSCLES 240 

to  lessen  tension  241 

to  lessen  tension  and  change  plane  242 

to  increase  tension 243 

to  increase  tension  and  change  plane  244 

objects  of  all  operations 310 

(See  the  various  "  phorias  "  and  "  tropias.") 


INDEX.  681 

ORBITAL  MALFORMATIONS   182 

OBLIQUE  MUSCLES, 

history  of  the  study  of 184 

simple  function  of 450 

complicated  function  of 452 

OBLIQUES,  INFERIOR, 

once  thought  to  be  advertors  504 

possibly  cut  by  Taylor  507 

OPTIC  Axis 10,  32,  528 

ORIENTATION 59,  74 

ORTHOPHORIA   146 

lateral,  tests  for 149,  152,  157 

vertical,  tests  for  150,  152,  3  57 

oblique,  tests  for 154,  161,  163,  250 

sthenic  176 

asthenic 177 

treatment  of 177 

PLANES  OF  REFERENCE 73 

median  fixed  plane 73 

horizontal  fixed  plane 73,  182 

PLANE  OF  ROTATION, 

how  to  construct 51 

PLANE  OF  ROTATION  OF  INDIVIDUAL  MUSCLES  51-57 

PAN  AS'  OPERATION 503 

PARALYSIS, 

of  the  third  nerve 600 

symptoms  of 600 

causes  of 598 

treatment  of 616 

of  the  fourth  nerve 602 

causes  of 598 

symptoms  of  —  , 602 


682  INDEX. 

PARALYSIS, 

treatment  of 616 

of  the  sixth  nerve  602 

causes  of 598 

symptoms  of  602 

treatment  of 616 

of  the  seventh  nerve 618 

PARALYSIS  AND  PARESIS, 

diagnosis  of 603 

rules  for  finding  the  affected  muscle 604,  605 

of  a  right-vertor 606 

of  a  left-vertor 607 

of  a  sub-vertor 608,  610 

of  a  supervertor 609,  610 

pose  of  the  head  in  611 

PARALYSIS, 

of  motion,  and  not  of  muscle 611 

symptoms  of 615 

PERIMETER, 

for  making  version  tests 168 

PERRY,  C.  H 398,  428 

PETIT    625 

POLES    27-33 

POLE,  POSTERIOR 10,  17,  19,  20,  24,  25,  94 

POLE,  ANTERIOR 10,  19,  20,  25,  27-35 

POLE,  SPACIAL,  MONOCULAR 17 

POLE,  BINOCULAR  124,  135 

PRESBYOPIA, 

causes  of 644,  650 

can  it  be  deferred?  650 

treatment  by  exercise 652 

treatment  by  correcting  lenses  655 


INDEX.  683 

PStUDO-ESOPHOBIA, 

how  manifested 646 

when  desirable  647 

when  harmful 647 

PSEUDO-EXOPHOBIA, 

how  manifested 648 

PBISMS, 

a  cause  of  compensating  heterotropia 492 

PBICE'S  CYCLO-PHOBOMETEB, 

the  first  made 160 

PBICE,  GEOBGE  H 253 

PHOBOMETEB, 

the  Stevens 147 

its  capabilities   148 

why  objectionable   148 

method  of  using 149 

the  Wilson, 

its  capabilities   152 

why  objectionable 148 

method  of  using 152 

the  correct  principle  of  construction  of  the 155 

the  Monocular 156 

QUEBIN   511 

RANNEY  209 

RETINAL  POINTS, 

law  of  corresponding 64 

RISLEY  182 

ROTATIONS, 

cardinal 7,  2i 

oblique 58 

monocular   39-63 

binocular   .  63-110 


684  INDEX. 

ROTATIONS, 

law  of 57,  59 

axis  of i,  2,  5,  10,  44,  45,     51 

plane  of l,  2,  5,  13,  19,     51 

by  a  single  muscle 51 

in  the  four  cardinal  directions 41,  77 

in  any  oblique  direction  41,  78,     79 

ROTATING  LINE 2,  4,  5,  6,     17 

ROTATING  POINT 4,  5,  6,     20 

ROTATING  POINTS,  Two 7 

RHYTHMIC  EXERCISE  OF  THE  MUSCLES 226 

STRABISMUS    497 

STEVENS'  NOMENCLATURE 146 

phororaeter   147 

clinoscope   160 

description  of   164 

tropometer   169 

STEVENS 182,  184,  209,  225 

STEELE,  N.  C 472 

SMITH,  PRIESTLEY 533,  635 

SHORTENING  OPERATIONS, 

advantages  of  257 

to  only  increase  tension 258 

to  alter  tension  and  change  plane 262 

marginal  262 

STROMEYEH   499 

SUB-DUCTION,  THE  NORMAL  153,  158,  198 

SUPERDUCTION,  THE  NORMAL  153,  158,  191 

SUPERVERSION  169,  171,  202 

SUB-VERSION    169,  172,  202 

SQUINT ......... 497 

SUPPRESSION,  MENTAL   66 


INDEX  685 

SYNERGISTS  AND  ANTAGONISTS, 

tables  of  59,  62 

old  table  59,  60 

new  table  62,  63 

TAYLOR,  THE  SQUINT  QUACK 505 

TESTS  FOR  HETEROPHORIA 189 

TENOTOMY, 
partial, 

central,  to  lower  tension  251 

marginal,  to  lower  tension  and  change  plane 256 

TENDONOMETER 254 

TSCHERNING   632 

TORSION, 

measured    47 

table  of  48,  50 

how  prevented 46 

TROPOMETER, 

description  of   169 

THORINGTON    303 

VERSION  POWER, 

standard  of 174 

VERSION  TEST, 

value  of 199 

by  tropometer 200 

by  perimeter  200 

VISUAL  Axis  8,  528 

VISUAL  LINES 14,  31,     35 

WILSON,  HAROLD 420 

WORTH  545 

YOUNG 629,  630 

ZONULA, 

how  relaxed  .  631 


Date  Due 


CAT.    NO.    23    233  PRINTED    IN    U.S.A. 


A  000510439 


WWU0o 

S263  o 
1911 


Savage,  Giles  C 

Ophthalmic  myology 


wwUoo 

S263  o 
1911 
Javage,  Giles  C 

Ophthalmic  myology  . . . 


MEDICAL  SCIENCES  LIBRARY 


